U.S. patent number 8,901,860 [Application Number 13/845,827] was granted by the patent office on 2014-12-02 for photovoltaic apparatus, maximum power point tracking control method and computer program in the same, and moving body including the same.
This patent grant is currently assigned to Sharp Kabushiki Kaisha. The grantee listed for this patent is Sharp Kabushiki Kaisha. Invention is credited to Kohichiroh Adachi, Masatomi Harada, Hiroshi Iwata, Kohtaroh Kataoka, Yoshiji Ohta, Yoshifumi Yaoi.
United States Patent |
8,901,860 |
Yaoi , et al. |
December 2, 2014 |
Photovoltaic apparatus, maximum power point tracking control method
and computer program in the same, and moving body including the
same
Abstract
A photovoltaic apparatus according to the present invention
includes a photovoltaic module and a tracking control device. The
photovoltaic module includes a plurality of series portions coupled
in parallel. The series portion includes a plurality of
photovoltaic elements coupled in series. The photovoltaic elements
coupled in a same straight row of the plurality of series portions
are coupled parallel to one another. The tracking control device is
configured to perform a maximum power point tracking control on an
output of the photovoltaic module. The photovoltaic module includes
a temperature sensor that detects a real panel temperature that is
a panel temperature when the photovoltaic module is operating.
Inventors: |
Yaoi; Yoshifumi (Osaka,
JP), Kataoka; Kohtaroh (Osaka, JP), Harada;
Masatomi (Osaka, JP), Adachi; Kohichiroh (Osaka,
JP), Ohta; Yoshiji (Osaka, JP), Iwata;
Hiroshi (Osaka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Sharp Kabushiki Kaisha |
Osaka |
N/A |
JP |
|
|
Assignee: |
Sharp Kabushiki Kaisha
(Osaka-shi, Osaka, JP)
|
Family
ID: |
49157004 |
Appl.
No.: |
13/845,827 |
Filed: |
March 18, 2013 |
Prior Publication Data
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|
Document
Identifier |
Publication Date |
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US 20130241448 A1 |
Sep 19, 2013 |
|
Foreign Application Priority Data
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Mar 19, 2012 [JP] |
|
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2012-062393 |
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Current U.S.
Class: |
318/139; 136/246;
136/244; 318/571; 318/572 |
Current CPC
Class: |
G05F
1/67 (20130101); H01L 31/02008 (20130101); Y02E
10/56 (20130101); Y02T 10/7072 (20130101) |
Current International
Class: |
H01L
31/042 (20140101) |
Field of
Search: |
;318/139,571,572
;136/244,246 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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8-153883 |
|
Jun 1996 |
|
JP |
|
2009-117658 |
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May 2009 |
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JP |
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2010-287795 |
|
Dec 2010 |
|
JP |
|
2011-206423 |
|
Oct 2011 |
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JP |
|
2011-222005 |
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Nov 2011 |
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JP |
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2012-039224 |
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Feb 2012 |
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JP |
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2012-060902 |
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Mar 2012 |
|
JP |
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2012-060906 |
|
Mar 2012 |
|
JP |
|
2012-169581 |
|
Sep 2012 |
|
JP |
|
Primary Examiner: Ip; Paul
Attorney, Agent or Firm: Nixon & Vanderhye, P.C.
Claims
What is claimed is:
1. A photovoltaic apparatus comprising: a photovoltaic module that
includes a plurality of series portions coupled in parallel, the
series portion including a plurality of photovoltaic elements
coupled in series, the photovoltaic elements coupled in a same
straight row of the plurality of series portions being coupled
parallel to one another; and a tracking control device configured
to perform a maximum power point tracking control on an output of
the photovoltaic module, wherein the photovoltaic module includes a
temperature sensor configured to detect a real panel temperature
when the photovoltaic module is operating, wherein the tracking
control device includes: a storage unit where a plurality of panel
temperature-output correlation characteristics are registered
corresponding to the panel temperature, the panel
temperature-output correlation characteristic preliminarily
specifying a correlation relationship between the panel temperature
and a characteristic of the output in the photovoltaic module; an
output characteristic selecting unit configured to: extract one of
the panel temperature-output correlation characteristics
corresponding to the real panel temperature among the plurality of
panel temperature-output correlation characteristics as a virtual
panel temperature-output correlation characteristic; and select a
maximum power operating voltage corresponding to a maximum output
in the virtual panel temperature-output correlation characteristic;
and a search start setting unit configured to extract an electric
power of the photovoltaic module when a voltage of the photovoltaic
module is set to a search start voltage higher than the maximum
power operating voltage, as a search electric power when a search
is started, wherein the tracking control device is configured to:
start a search using the search start voltage and the search
electric power when the search is started as references; and
extract a maximum power point of the photovoltaic module at the
real panel temperature.
2. The photovoltaic apparatus according to claim 1, wherein the
photovoltaic module employs a distributed arrangement where a
layout pattern of the photovoltaic elements is different from an
arrangement in an equivalent circuit.
3. The photovoltaic apparatus according to claim 1, wherein the
tracking control device includes: a search processor configured to
extract the electric power of the photovoltaic module as a search
electric power for search, the electric power being obtained when a
voltage of the photovoltaic module is sequentially decreased from
the search start voltage by a preliminarily set search unit voltage
every time so as to be set to a search voltage for search; a search
power comparator configured to compare the search electric power
before the voltage of the photovoltaic module is decreased by the
search unit voltage with the search electric power when the voltage
of the photovoltaic module is decreased by the search unit voltage;
and a search control unit configured to: set the voltage of the
photovoltaic module before decreasing by the search unit voltage to
a maximum power operating voltage at the real panel temperature and
terminate the search in a case where the search electric power
before the voltage of the photovoltaic module is decreased by the
search unit voltage is higher than the search electric power when
the voltage of the photovoltaic module is decreased by the search
unit voltage; and replace the search electric power before
decreasing by the search unit voltage with the search electric
power when decreased by the search unit voltage so as to perform a
process in the search power comparator in a case where the search
electric power before the voltage of the photovoltaic module is
decreased by the search unit voltage is lower than the search
electric power when the voltage of the photovoltaic module is
decreased by the search unit voltage.
4. The photovoltaic apparatus according to claim 1, wherein the
panel temperature-output correlation characteristic registered in
the storage unit associates the panel temperature with the maximum
power operating voltage, the maximum power operating voltage
corresponding to the maximum output obtained by a preliminarily
assumed lighting intensity at the panel temperature.
5. The photovoltaic apparatus according to claim 4, wherein in a
case where the real panel temperature is different from the panel
temperature registered in the storage unit, the output
characteristic selecting unit extracts the panel temperature-output
correlation characteristic corresponding to the panel temperature
that is lower than and closest to the real panel temperature among
the panel temperatures registered in the storage unit as the
virtual panel temperature-output correlation characteristic.
6. The photovoltaic apparatus according to claim 1, wherein the
search start voltage is calculated by a formula for computation,
the formula for computation being preliminarily specified with
respect to the maximum power operating voltage.
7. The photovoltaic apparatus according to claim 6, wherein the
formula for computation is used to obtain the search start voltage
by multiplying the maximum power operating voltage by a coefficient
larger than one.
8. The photovoltaic apparatus according to claim 6, wherein the
formula for computation is used to obtain the search start voltage
based on an open circuit voltage of the photovoltaic module and the
maximum power operating voltage.
9. The photovoltaic apparatus according to claim 3, wherein the
search unit voltage is set to be smaller than 1/2 of difference
between the maximum power operating voltage and the search start
voltage.
10. A moving body for running with a motor comprising: a
photovoltaic apparatus that includes a photovoltaic module and a
tracking control device configured to perform a maximum power point
tracking control on an output of the photovoltaic module; a cell
power supply charged by the photovoltaic apparatus; and a motor
configured to operate with electric power supplied from the cell
power supply, wherein the photovoltaic apparatus is the
photovoltaic apparatus according to claim 1.
11. A maximum power point tracking control method in a photovoltaic
apparatus, wherein the photovoltaic apparatus includes: a
photovoltaic module that includes a plurality of series portions
coupled in parallel, the series portion including a plurality of
photovoltaic elements coupled in series, the photovoltaic elements
coupled in a same straight row of the plurality of series portions
being coupled parallel to one another; and a tracking control
device configured to perform a maximum power point tracking control
on an output of the photovoltaic module, wherein the photovoltaic
module includes a temperature sensor configured to detect a real
panel temperature when the photovoltaic module is operating,
wherein the tracking control device includes: a storage unit where
a plurality of panel temperature-output correlation characteristics
are registered corresponding to the panel temperature, the panel
temperature-output correlation characteristic preliminarily
specifying a correlation relationship between the panel temperature
and the output characteristic in the photovoltaic module; an output
characteristic selecting unit; and a search start setting unit,
wherein the maximum power point tracking control method comprises:
a step of detecting a real panel temperature by the temperature
sensor; a step of extracting one of the panel temperature-output
correlation characteristics corresponding to the real panel
temperature among the plurality of panel temperature-output
correlation characteristics as a virtual panel temperature-output
correlation characteristic, and selecting a maximum power operating
voltage corresponding to a maximum output in the virtual panel
temperature-output correlation characteristic by the output
characteristic selecting unit; a step of extracting an electric
power of the photovoltaic module when a voltage of the photovoltaic
module is set to a search start voltage higher than the maximum
power operating voltage, as a search electric power when a search
is started, by the search start setting unit; and a step of
starting a search using the search start voltage and the search
electric power when the search is started as references, and
extracting a maximum power point of the photovoltaic module at the
real panel temperature by the tracking control device.
12. A computer program for a computer to execute a maximum power
point tracking control in a photovoltaic apparatus, wherein the
photovoltaic apparatus includes: a photovoltaic module that
includes a plurality of series portions coupled in parallel, the
series portion including a plurality of photovoltaic elements
coupled in series, the photovoltaic elements coupled in a same
straight row of the plurality of series portions being coupled
parallel to one another; and a tracking control device configured
to perform a maximum power point tracking control on an output of
the photovoltaic module, wherein the photovoltaic module includes a
temperature sensor configured to detect a real panel temperature
when the photovoltaic module is operating, wherein the tracking
control device includes: a storage unit where a plurality of panel
temperature-output correlation characteristics are registered
corresponding to the panel temperature, the panel
temperature-output correlation characteristic preliminarily
specifying a correlation relationship between the panel temperature
and the output characteristic in the photovoltaic module; an output
characteristic selecting unit; and a search start setting unit,
wherein the computer program causes a computer to execute: a step
of detecting a real panel temperature using the temperature sensor
by the tracking control device; a step of extracting one of the
panel temperature-output correlation characteristics corresponding
to the real panel temperature among the plurality of panel
temperature-output correlation characteristics as a virtual panel
temperature-output correlation characteristic, and selecting a
maximum power operating voltage corresponding to a maximum output
in the virtual panel temperature-output correlation characteristic
by the output characteristic selecting unit; a step of extracting
an electric power of the photovoltaic module when a voltage of the
photovoltaic module is set to a search start voltage higher than
the maximum power operating voltage, as a search electric power
when a search is started, by the search start setting unit; and a
step of starting a search using the search start voltage and the
search electric power when the search is started as references, and
extracting a maximum power point of the photovoltaic module at the
real panel temperature by the tracking control device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on and claims priority under 35 U.S.C.
.sctn.119 (a) to Japanese Patent Application 2012-062393, filed on
Mar. 19, 2012, the entire content of which is incorporated herein
by reference.
FIELD
The present invention relates to a photovoltaic apparatus including
a photovoltaic module, a maximum power point tracking control
method and a computer program in the photovoltaic apparatus, and a
moving body.
DESCRIPTION OF THE RELATED ART
In a solar cell module, since an output characteristic (a
power-voltage characteristic) has a peak, an operation at the
maximum power point is achieved by a maximum power point tracking
control (MPPT control).
By referring to FIG. 21 and FIG. 22, a description will be given of
a known maximum power point tracking control. FIG. 21 is a
characteristic graph illustrating an exemplary MPPT control in a
normal output characteristic of a general solar cell module.
In a state of usual sunshine, the output characteristic illustrates
a single-peaked curve. Accordingly, the MPPT control simply
performs a search Tr1 and a search Tr2 from low voltage toward high
voltage (an open circuit voltage Voc side) to extract the maximum
power point MPP.
That is, a folding point of the search Tr1, which is a rising
track, and the search Tr2, which is a falling track, is extracted
as the maximum power point MPP. However, a sweep range Vsp where
the search is performed is a wide range from low voltage to high
voltage. This makes quick MPPT control difficult. Additionally, the
wide sweep range Vsp causes a problem of high power consumption in
the control system.
FIG. 22 is a characteristic graph illustrating an exemplary MPPT
control with an output characteristic affected by shade in a
general solar cell module.
In the known solar cell module, the shade may considerably change
the output characteristic and cause, for example, two peaks. In
this case, the MPPT control detects a rising track Tr3 and a
falling track Tr4 regarding a peak formed at the higher voltage
side in addition to the rising track Tr1 and the falling track Tr2
so as to detect the maximum power point MPP. Accordingly, the known
problem becomes more obvious.
Regarding a maximum power point tracking control method by a known
hill-climbing method, Japanese Unexamined Patent Application
Publication No. 2009-117658 is known.
The present invention has been made in view of the above-described
circumstances, and it is an object of the present invention to
provide a photovoltaic apparatus that ensures a maximum power point
tracking control almost without being affected by shade.
Additionally, another object of the present invention is to provide
a maximum power point tracking control method and a computer
program that improves the photovoltaic apparatus according to the
present invention to operate more effectively.
Additionally, another object of the present invention is to provide
a moving body that employs the photovoltaic apparatus according to
the present invention to eliminate the impact of shade during
running, so as to ensure a stable and efficient electric generation
and running.
SUMMARY OF THE INVENTION
A photovoltaic apparatus according to the present invention is
based on the premise that a photovoltaic apparatus that includes a
photovoltaic module and a tracking control device. The photovoltaic
module includes a plurality of series portions coupled in parallel.
The series portion includes a plurality of photovoltaic elements
coupled in series. The photovoltaic elements coupled in a same
straight row of the plurality of series portions are coupled
parallel to one another. The tracking control device is configured
to perform a maximum power point tracking control on an output of
the photovoltaic module. The photovoltaic apparatus is
characterized by the following. That is, the photovoltaic module
includes a temperature sensor configured to detect a real panel
temperature when the photovoltaic module is operating. The tracking
control device includes a storage unit where a plurality of panel
temperature-output correlation characteristics are registered
corresponding to the panel temperature, an output characteristic
selecting unit, and a search start setting unit. The panel
temperature-output correlation characteristic preliminarily
specifies a correlation relationship between the panel temperature
and a characteristic of the output in the photovoltaic module. The
output characteristic selecting unit is configured to: extract one
of the panel temperature-output correlation characteristics
corresponding to the real panel temperature among the plurality of
panel temperature-output correlation characteristics as a virtual
panel temperature-output correlation characteristic; and extract a
maximum power operating voltage corresponding to a maximum output
in the virtual panel temperature-output correlation characteristic.
The search start setting unit is configured to select an electric
power of the photovoltaic module when a voltage of the photovoltaic
module is set to a search start voltage higher than the maximum
power operating voltage, as a search electric power when a search
is started. The tracking control device is configured to: start a
search using the search start voltage and the search electric power
when the search is started as references; and extract a maximum
power point of the photovoltaic module at the real panel
temperature.
Accordingly, the photovoltaic apparatus according to the present
invention detects the real panel temperature of the photovoltaic
module, and extracts one of the panel temperature-output
correlation characteristics corresponding to the real panel
temperature as the virtual panel temperature-output correlation
characteristic. The photovoltaic apparatus sets the voltage of the
photovoltaic module to the search start voltage higher than the
maximum power operating voltage in the virtual panel
temperature-output correlation characteristic, and starts a search
using the search start voltage and the search electric power when
the search is started as references to perform the maximum power
point tracking control. This allows a simple and accurate setting
of the maximum power operating voltage in the detected real panel
temperature with a search in a narrow range. This photovoltaic
apparatus simply, accurately, and quickly tracks (searches) the
maximum power point in the output characteristic of the
photovoltaic module.
In the above-described configuration, the photovoltaic apparatus
according to the present invention may employ a distributed
arrangement where a layout pattern of the photovoltaic elements is
different from an arrangement in an equivalent circuit.
In this configuration, the photovoltaic apparatus according to the
present invention employs a distributed arrangement as the layout
pattern of the photovoltaic elements that constitute the
photovoltaic module so as to suppress the impact of shade on the
series portion where the photovoltaic elements are coupled in
series. This suppresses a decrease in power transmission
efficiency, thus improving power extraction efficiency.
Additionally, the photovoltaic apparatus according to the present
invention may be configured as follows. The tracking control device
may include a search processor, a search power comparator, and a
search control unit. The search processor is configured to extract
the electric power of the photovoltaic module as a search electric
power for search. The electric power is obtained when a voltage of
the photovoltaic module is sequentially decreased from the search
start voltage by a preliminarily set search unit voltage every time
so as to be set to a search voltage for search. The search power
comparator is configured to compare the search electric power
before the voltage of the photovoltaic module is decreased by the
search unit voltage with the search electric power when the voltage
of the photovoltaic module is decreased by the search unit voltage.
The search control unit configured to: set the voltage of the
photovoltaic module before decreasing by the search unit voltage to
a maximum power operating voltage at the real panel temperature and
terminate the search in a case where the search electric power
before the voltage of the photovoltaic module is decreased by the
search unit voltage is higher than the search electric power when
the voltage of the photovoltaic module is decreased by the search
unit voltage; and replace the search electric power before
decreasing by the search unit voltage with the search electric
power when decreased by the search unit voltage so as to perform a
process in the search power comparator in a case where the search
electric power before the voltage of the photovoltaic module is
decreased by the search unit voltage is lower than the search
electric power when the voltage of the photovoltaic module is
decreased by the search unit voltage.
With this configuration, the photovoltaic apparatus according to
the present invention sequentially decreases the voltage from the
search start voltage by the preliminarily set search unit voltage
to be set to the search voltage for search, and compares the search
electric powers before and after the search voltage is varied by
the search unit voltage to perform the maximum power point tracking
control. This allows an efficient and quick setting of the maximum
power operating voltage with respect to the real panel temperature
by the search in the preliminarily set narrow range. Thus, even in
the case where the irradiation state of the light is frequently
varied, this allows a simple, accurate, and quick tracking of the
maximum power point in the output characteristic of the
photovoltaic module.
In the photovoltaic apparatus according to the present invention,
the panel temperature-output correlation characteristic registered
in the storage unit may associate the panel temperature with the
maximum power operating voltage that corresponds to the maximum
output obtained by a preliminarily assumed lighting intensity at
the panel temperature.
With this configuration, the photovoltaic apparatus according to
the present invention directly associates the panel temperature
with the maximum power operating voltage corresponding to the
maximum output at the panel temperature in the panel
temperature-output correlation characteristic. Use of the virtual
panel temperature-output correlation characteristic corresponding
to the detected real panel temperature allows an accurate and quick
direct extraction of the maximum power operating voltage of the
photovoltaic module. This allows an accurate and quick selection of
the search start voltage to perform an accurate and quick maximum
power point tracking control.
In the photovoltaic apparatus according to the present invention,
in a case where the real panel temperature is different from the
panel temperature registered in the storage unit, the output
characteristic selecting unit is preferred to extract the panel
temperature-output correlation characteristic corresponding to the
panel temperature that is lower than and closest to the real panel
temperature among the panel temperatures registered in the storage
unit as the virtual panel temperature-output correlation
characteristic.
With this configuration, the photovoltaic apparatus according to
the present invention extracts the panel temperature-output
correlation characteristic corresponding to the panel temperature
that is lower than and closest to the real panel temperature among
the panel temperatures registered in the storage unit as the
virtual panel temperature-output correlation characteristic. This
allows an extraction of the virtual panel temperature-output
correlation characteristic to limit a search range of any real
panel temperature to a narrow range and perform the maximum power
point tracking control.
In the photovoltaic apparatus according to the present invention,
the search start voltage may be calculated by a formula for
computation. The formula for computation is preliminarily specified
with respect to the maximum power operating voltage.
With this configuration, the photovoltaic apparatus according to
the present invention calculates the search start voltage by
applying the formula for computation to the maximum power operating
voltage in the virtual panel temperature-output correlation
characteristic. This allows obtaining the search start voltage
accurately and quickly even in any irradiation state of the
photovoltaic module.
In the photovoltaic apparatus according to the present invention,
the formula for computation may be used to obtain the search start
voltage by multiplying the maximum power operating voltage by a
coefficient larger than one.
With this configuration, the photovoltaic apparatus according to
the present invention obtains the search start voltage by
multiplying the maximum power operating voltage by a coefficient
larger than one. With any specification of the maximum power
operating voltage of the photovoltaic module, this suppresses the
impact of the specification to extract an accurate search start
voltage.
In the photovoltaic apparatus according to the present invention,
the formula for computation may be used to obtain the search start
voltage based on an open circuit voltage of the photovoltaic module
and the maximum power operating voltage.
With this configuration, the photovoltaic apparatus according to
the present invention can apply the formula for computation where
the search start voltage is arranged between the maximum power
operating voltage and the open circuit voltage. The maximum power
operating voltage is known to have a constant relation to the open
circuit voltage. This allows a simple and highly accurate
calculation of the search start voltage.
In the photovoltaic apparatus according to the present invention,
it is preferred that the search unit voltage be set to be smaller
than 1/2 of difference between the maximum power operating voltage
and the search start voltage.
With this configuration, the photovoltaic apparatus according to
the present invention sets the search unit voltage to a value
smaller than 1/2 of the difference between the maximum power
operating voltage and the search start voltage. Accordingly, when a
search is performed such that the search voltage is shifted from
the search start voltage to the maximum power operating voltage
side, the configuration allows performing at least a plurality of
searches between the search start voltage and the maximum power
operating voltage. This ensures a highly accurate and quick
search.
A maximum power point tracking control method according to the
present invention is based on the premise that a photovoltaic
apparatus that includes a photovoltaic module and a tracking
control device. The photovoltaic module includes a plurality of
series portions coupled in parallel. The series portion includes a
plurality of photovoltaic elements coupled in series. The
photovoltaic elements coupled in a same straight row of the
plurality of series portions are coupled parallel to one another.
The tracking control device is configured to perform a maximum
power point tracking control on an output of the photovoltaic
module. The photovoltaic apparatus is characterized by the
following. That is, the photovoltaic module includes a temperature
sensor configured to detect a real panel temperature when the
photovoltaic module is operating. The tracking control device
includes a storage unit where a plurality of panel
temperature-output correlation characteristics are registered
corresponding to the panel temperature, an output characteristic
selecting unit, and a search start setting unit. The panel
temperature-output correlation characteristic preliminarily
specifies a correlation relationship between the panel temperature
and the output characteristic in the photovoltaic module. The
maximum power point tracking control method includes: a step of
detecting a real panel temperature by the temperature sensor; a
step of extracting one of the panel temperature-output correlation
characteristics corresponding to the real panel temperature among
the plurality of panel temperature-output correlation
characteristics as a virtual panel temperature-output correlation
characteristic, and selecting a maximum power operating voltage
corresponding to a maximum output in the virtual panel
temperature-output correlation characteristic by the output
characteristic selecting unit; a step of extracting an electric
power of the photovoltaic module when a voltage of the photovoltaic
module is set to a search start voltage higher than the maximum
power operating voltage, as a search electric power when a search
is started, by the search start setting unit; and a step of
starting a search using the search start voltage and the search
electric power when the search is started as references, and
extracting a maximum power point of the photovoltaic module at the
real panel temperature by the tracking control device.
Thus, the maximum power point tracking control method according to
the present invention includes: detecting a real panel temperature
of the photovoltaic module; selecting a maximum power operating
voltage corresponding to a maximum output in the virtual panel
temperature-output correlation characteristic; extracting an
electric power of the photovoltaic module when a voltage of the
photovoltaic module is set to a search start voltage higher than
the maximum power operating voltage as a search electric power when
a search is started; then starting a search using the search start
voltage and the search electric power when the search is started as
references; and extracting the maximum power point of the
photovoltaic module at the real panel temperature. This allows a
simple and accurate setting of the maximum power operating voltage
at the detected real panel temperature with a search in a narrow
range, thus ensuring a simple, accurate, and quick tracking
(searching) of the maximum power point of the output characteristic
in the photovoltaic module.
A computer program according to the present invention is based on
the premise that the computer program for a computer to execute a
maximum power point tracking control in a photovoltaic apparatus
that includes a photovoltaic module and a tracking control device.
The photovoltaic module includes a plurality of series portions
coupled in parallel. The series portion includes a plurality of
photovoltaic elements coupled in series. The photovoltaic elements
coupled in a same straight row of the plurality of series portions
are coupled parallel to one another. The tracking control device is
configured to perform a maximum power point tracking control on an
output of the photovoltaic module. The photovoltaic apparatus is
characterized by the following. That is, the photovoltaic module
includes a temperature sensor configured to detect a real panel
temperature when the photovoltaic module is operating. The tracking
control device includes a storage unit where a plurality of panel
temperature-output correlation characteristics are registered
corresponding to the panel temperature, an output characteristic
selecting unit and a search start setting unit. The panel
temperature-output correlation characteristic preliminarily
specifies a correlation relationship between the panel temperature
and the output characteristic in the photovoltaic module. The
computer program for a computer executes: a step of detecting a
real panel temperature using the temperature sensor by the tracking
control device; a step of extracting one of the panel
temperature-output correlation characteristics corresponding to the
real panel temperature among the plurality of panel
temperature-output correlation characteristics as a virtual panel
temperature-output correlation characteristic, and selecting a
maximum power operating voltage corresponding to a maximum output
in the virtual panel temperature-output correlation characteristic
by the output characteristic selecting unit; a step of extracting
an electric power of the photovoltaic module when a voltage of the
photovoltaic module is set to a search start voltage higher than
the maximum power operating voltage, as a search electric power
when a search is started, by the search start setting unit; and a
step of starting a search using the search start voltage and the
search electric power when the search is started as references, and
extracting a maximum power point of the photovoltaic module at the
real panel temperature by the tracking control device.
Accordingly, the computer program according to the present
invention makes the computer execute the maximum power point
tracking control method in the photovoltaic apparatus according to
the present invention. This allows a simple and accurate setting of
the maximum power operating voltage at the detected real panel
temperature by a search in a narrow range, thus ensuring a simple,
accurate, and quick tracking (searching) of the maximum power point
of the output characteristic in the photovoltaic module.
A moving body according to the present invention includes a
photovoltaic apparatus, a cell power supply, and a motor. The
photovoltaic apparatus includes a photovoltaic module and a
tracking control device configured to perform a maximum power point
tracking control on an output of the photovoltaic module. The cell
power supply is charged by the photovoltaic apparatus. The motor is
configured to operate with electric power supplied from the cell
power supply. The photovoltaic apparatus is the photovoltaic
apparatus according the present invention.
Accordingly, the moving body according to the present invention
includes the photovoltaic apparatus. The photovoltaic apparatus
operates with the maximum output by the maximum power point
tracking control corresponding to the real panel temperature that
is the panel temperature when the photovoltaic module is operating.
The moving body performs a quick and efficient maximum power point
tracking control by suppressing power consumption in the control
system caused by the maximum power point tracking control. This
eliminates the impact of the shade during running to ensure a
stable efficient electric generation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an equivalent circuit of a known photovoltaic module
illustrating a principle of a photovoltaic module to be applied to
the present invention;
FIG. 2 is a pattern diagram schematically illustrating a layout
pattern in the photovoltaic module illustrated in FIG. 1 and an
assumed shade;
FIG. 3 is an equivalent circuit of a photovoltaic module to be
applied to the present invention;
FIG. 4 is a pattern diagram schematically illustrating a layout
pattern in the photovoltaic module illustrated in FIG. 3 and an
assumed shade;
FIG. 5 is an equivalent circuit of a photovoltaic module to be
applied to the present invention;
FIG. 6 is a pattern diagram schematically illustrating a layout
pattern of the photovoltaic module illustrated in FIG. 5 and an
assumed shade;
FIG. 7 is an equivalent circuit of the known photovoltaic module in
another embodiment;
FIG. 8 is a pattern diagram schematically illustrating a layout
pattern of the photovoltaic module illustrated in FIG. 7 and an
assumed shade SH;
FIG. 9 is an equivalent circuit of a photovoltaic module to be
applied to the present invention;
FIG. 10 is a pattern diagram schematically illustrating a layout
pattern of the photovoltaic module illustrated in FIG. 9 and an
assumed shade;
FIG. 11 is a pattern diagram illustrating a coupling condition of
photovoltaic elements in a photovoltaic module to be applied to
Embodiment 1 of the present invention;
FIG. 12 is a characteristic graph illustrating a relationship of
extracted electric energy to an irradiated area rate in the
photovoltaic module illustrated FIG. 11;
FIG. 13 is a graph of an output characteristic illustrating
variation in output with respect to an output characteristic (a
power-voltage characteristic) of the photovoltaic module
illustrated in FIG. 11 in the case where a shaded condition is used
as a parameter;
FIG. 14 is a characteristic graph illustrating variation in output
with respect to the output characteristic (the power-voltage
characteristic) of the photovoltaic module illustrated in FIG. 11
in the case where a temperature condition is used as a
parameter;
FIG. 15 is a data table illustrating an example where data is
obtained as a panel temperature-output correlation characteristic
with respect to the output characteristic illustrated in FIG. 14 to
make listed data;
FIG. 16 is a data table illustrating a modification of the panel
temperature-output correlation characteristic where data is
obtained as a panel temperature-output correlation characteristic
with respect to the output characteristic illustrated in FIG. 14 to
make listed data;
FIG. 17 is a block diagram illustrating an overall configuration of
a photovoltaic apparatus according to Embodiment 2 of the present
invention mainly using functional blocks;
FIG. 18 is a flowchart illustrating an operation process in a
tracking control device that constitutes a main portion of the
photovoltaic apparatus illustrated in FIG. 17;
FIG. 19 is a graph illustrating a state of a maximum power point
tracking control in the tracking control device that constitutes
the main portion of the photovoltaic apparatus illustrated in FIG.
17;
FIG. 20 is a block diagram illustrating functional blocks of a
moving body according to Embodiment 3 of the present invention;
FIG. 21 is a characteristic graph illustrating an exemplary MPPT
control with a normal output characteristic of a general solar cell
module; and
FIG. 22 is a characteristic graph illustrating an exemplary MPPT
control with an output characteristic affected by a shade in the
general solar cell module.
DETAILED DESCRIPTION
Hereinafter, embodiments according to the present invention will be
described by referring to the accompanying drawings. First, a
principle of the invention will be described. Subsequently, the
embodiments will be described.
(Configuration, and Operation and Effect of a Photovoltaic Module
to be Applied to the Present Invention)
First, a principle (configuration, operation and effect) of a
photovoltaic module to be applied to the present invention will be
described by referring to FIG. 1 to FIG. 10.
FIG. 1, FIG. 2, FIG. 7, and FIG. 8 relate to a known photovoltaic
module MA. FIG. 3, FIG. 4, FIG. 9, and FIG. 10 relate to a
photovoltaic module MB to be applied to the present invention. FIG.
5 and FIG. 6 relate to a photovoltaic module MC to be applied to
the present invention. The photovoltaic module MC is a further
improvement of the photovoltaic module MB.
First, by referring to FIG. 1 to FIG. 6, a configuration, operation
and effect of the photovoltaic module MB to be applied to the
present invention will be described compared with the known
photovoltaic module MA. Additionally, a configuration, operation
and effect of the photovoltaic module MC to be applied to the
present invention will be described compared with the photovoltaic
module MB.
FIG. 1 is an equivalent circuit of the known photovoltaic module MA
illustrating principles of the photovoltaic module MB and the
photovoltaic module MC to be applied to the present invention.
FIG. 2 is a pattern diagram schematically illustrating a layout
pattern in the photovoltaic module MA illustrated in FIG. 1 and an
assumed shade SH.
The known photovoltaic module MA includes a series portion DS
formed of a plurality (for example, three) of photovoltaic elements
D coupled in series (for convenience of explanation, individual
reference numerals are given to the respective photovoltaic
elements so as to express the elements in forms of D1a, D2a-D3d.
Especially, in the case where distinguishing respective
photovoltaic elements is unnecessary, these elements may be
described simply as photovoltaic elements D. Hereinafter, the same
applies to the photovoltaic module MB and the photovoltaic module
MC).
The photovoltaic module MA includes a series portion DS constituted
by photovoltaic elements D1a, D2a, and D3a, a series portion DS
constituted by photovoltaic elements D1b, D2b, and D3b, a series
portion DS constituted by photovoltaic elements D1c, D2c, and D3c,
and a series portion DS constituted by photovoltaic elements D1d,
D2d, D3d. That is, the photovoltaic module MA includes four series
portions DS.
Both ends of the four series portions DS are coupled parallel to
one another. Accordingly, the photovoltaic module MA includes 12
photovoltaic elements D with three elements in series and four
elements in parallel. In the photovoltaic module MA, each series
portion DS is electrically insulated and separated from the other
series portions DS to form an independent series element group.
The layout pattern of the photovoltaic element D is assumed to be
shaded by the shade SH (FIG. 2). That is, the shade SH shades the
photovoltaic element D2c and the photovoltaic element D2d.
Accordingly, the photovoltaic element D2c and the photovoltaic
element D2d are in a non-generation state and do not pass current
(In the equivalent circuit of FIG. 1, the shade SH is
overlapped.).
Since current does not flow into the photovoltaic element D2c, the
series portion DS constituted by the photovoltaic elements D1c,
D2c, and D3c cannot generate electric power as a whole even though
the photovoltaic elements D1c and D3c are exposed to light.
Additionally, since current does not flow into the photovoltaic
element D2d, the series portion DS constituted by the photovoltaic
elements D1d, D2d, and D3d cannot generate electric power as a
whole although the photovoltaic elements D1d and D3d are exposed to
light. That is, only two series portions DS on the left side ensure
a generation state.
Accordingly, the photovoltaic module MA has a generating area rate
(a ratio of an area in generation state, which contributes to
effective output, to the whole area) of 6/12 (=0.5=50%) despite an
irradiated area rate of 10/12 (=0.83). Power generation efficiency
with respect to the area is 50%, which is low.
FIG. 3 is an equivalent circuit of a photovoltaic module MB to be
applied to the present invention. FIG. 4 is a pattern diagram
schematically illustrating a layout pattern in the photovoltaic
module MB illustrated in FIG. 3 and the assumed shade SH.
The photovoltaic module MB includes a series portion DS formed of a
plurality (for example, three) of photovoltaic elements D coupled
in series. That is, similarly to the photovoltaic module MA, the
photovoltaic module MB includes a series portion DS constituted by
photovoltaic elements D1a, D2a, and D3a, a series portion DS
constituted by photovoltaic elements D1b, D2b, and D3b--a series
portion DS constituted by photovoltaic elements D1h, D2h, and D3h.
That is, the photovoltaic module MB includes eight series portions
DS.
Both ends of the eight series portions DS are coupled parallel to
one another. Accordingly, the photovoltaic module MB includes 24
photovoltaic elements D with three elements in series and eight
elements in parallel.
In the photovoltaic module MB, unlike the photovoltaic module MA,
the photovoltaic elements D coupled (arranged) in the same straight
row in the respective series portions DS are coupled parallel to
one another via parallel wiring Wp. That is, the photovoltaic
module MB has a structure where parallel contact points are formed
in a row direction in addition to series contact points in the
series portion DS in a column direction. The structure includes
two-dimensional contact points where contact points are formed in
both directions of the row direction and the column direction.
In the case where the whole area of a photo-receiving surface in
the photovoltaic module MA and the whole area of a photo-receiving
surface in the photovoltaic module MB are the same, the
photovoltaic module MB includes twice the number of photovoltaic
elements D. This allows the number of photovoltaic elements D in
generation state to follow a shape of the shade SH with high
accuracy.
Assume that the layout pattern of the photovoltaic elements D is
shaded by the shade SH (FIG. 4). That is, the shade SH shades the
photovoltaic element D2f, the photovoltaic element D2g, and the
photovoltaic element D2h. Accordingly, the photovoltaic element
D2f, the photovoltaic element D2g, and the photovoltaic element D2h
are in a non-generation state and do not pass current (In the
equivalent circuit of FIG. 3, the shade SH is overlapped.).
In the photovoltaic module MA, the shade SH affects two elements of
the photovoltaic elements D2c and D2d (which is 1/2 with respect to
four elements of the photovoltaic elements D2a, D2b, D2c, and D2d)
(see FIG. 1 and FIG. 2). For example, even in the case where the
shade SH affects the entire photovoltaic element D2d and
approximately half of the photovoltaic element D2c, the
photovoltaic element D2c is also affected. Accordingly, two
elements of the photovoltaic elements D2c and D2d are substantially
assumed to be affected. In contrast, in the case of the
photovoltaic module MB, the following case is assumed. The
photovoltaic element D2e is not affected by the shade SH while
three elements of the photovoltaic elements D2f, D2g, and D2h are
affected by the shade SH.
That is, among eight elements of the photovoltaic elements D2a-D2h,
three elements of the photovoltaic elements D2f, D2g, and D2h are
affected by the shade SH. This decreases the number of the series
portions DS affected by the shade SH to 3/8 (<1/2). This
suppresses the impact of the shade SH and ensures an advantage (an
advantage that suppresses the impact of the shade SH) with respect
to the known photovoltaic module MA. The entire current is
restricted by a straight row where the number of photovoltaic
elements D in generation state is smallest among the respective
straight rows. That is, the number of the series portions in
operation is determined by the minimum number of photovoltaic
elements D in a generation state in the respective straight
rows.
In the photovoltaic module MB illustrated in FIG. 3 and FIG. 4, the
middle row includes the minimum number of the photovoltaic elements
D in a generation state. That is, among the photovoltaic elements
D2a-D2e, D2f, D2g, and D2h, current flows through the photovoltaic
element D2a-D2e (five photovoltaic elements D in the middle row).
The entire effective electric generation is controlled by the
photovoltaic elements D (with a generating area of 5.times.3=15)
corresponding to five columns and three rows of the photovoltaic
elements D2a-D2e. The rate of the generating area to the whole area
becomes 15/24.
Accordingly, the photovoltaic module MB has an irradiated area rate
of 21/24 (=0.875 that is higher than 0.83 of the photovoltaic
module MA), and a generating area rate of 15/24 (=0.625=62.5%), and
a power generation efficiency of 62.5% with respect to the whole
area. That is, the photovoltaic module MB ensures the generating
area rate higher than that of the photovoltaic module MA, and
improves power extraction efficiency to ensure high power
generation efficiency. The advantage of the photovoltaic module MB
according to the present invention with respect to the known
photovoltaic module MA will be described by additionally applying
concrete examples in FIG. 7 to FIG. 10.
FIG. 5 is an equivalent circuit of a photovoltaic module MC to be
applied to the present invention. FIG. 6 is a pattern diagram
schematically illustrating a layout pattern of the photovoltaic
module MC illustrated in FIG. 5 and an assumed shade SH.
The photovoltaic module MC is a further improvement of the
photovoltaic module MB. Accordingly, differences will mainly be
described.
The photovoltaic module MC includes a series portion DS formed of a
plurality (for example, three) of photovoltaic elements D coupled
in series. The photovoltaic elements D coupled (arranged) in the
same straight row in the respective series portions DS are coupled
parallel to one another via parallel wiring Wp as a coupling form
with two-dimensional contact points. Additionally, the photovoltaic
module MC includes the photovoltaic elements D with an arrangement
(a layout pattern) that is an arrangement different from an
arrangement in an equivalent circuit (that is, in a state of a
distributed arrangement where the elements are randomly and
decentrally arranged) in addition to the coupling form with the
two-dimensional contact points.
In the case where the photovoltaic elements D are randomly and
decentrally arranged, the photovoltaic elements D are arranged in
the upper row in the equivalent circuit while the photovoltaic
elements D are decentrally arranged in any of the upper row, the
middle row, and the lower row in the layout pattern. Additionally,
the photovoltaic elements D are arranged in the same straight row
in the equivalent circuit, while the photovoltaic elements D in the
layout pattern are decentrally arranged in different lateral
positions from those in the equivalent circuit.
The inventors refer to the form (the photovoltaic module MC)
including the coupling form (the photovoltaic module MB and the
photovoltaic module MC) with the two-dimensional contact points and
the architecture where the arrangement (the layout pattern) of the
photovoltaic elements is an arrangement different from the
arrangement in the equivalent circuit as "distributed arrangement
architecture." With this distributed arrangement, even in the case
where the shade SH concentrates on the layout, the shade SH is
decentrally arranged on the equivalent circuit. This suppresses the
impact of the shade SH on the series portion DS where the elements
are coupled in series.
The photovoltaic module MC is as illustrated in the equivalent
circuit. In the upper row, the photovoltaic element D1a, the
photovoltaic element D2b--the photovoltaic element D1h are coupled
in parallel. In the middle row, the photovoltaic element D2a, the
photovoltaic element D2b--the photovoltaic element D2h are coupled
in parallel. In the lower row, the photovoltaic element D3a, the
photovoltaic element D3b--the photovoltaic element D3h are
arranged. The coupling condition of the equivalent circuit is
similar to that of the photovoltaic module MB.
The coupling conditions of the photovoltaic elements D in the
equivalent circuit of the photovoltaic module MB and in the
equivalent circuit of the photovoltaic module MC are the same. In
contrast, in the layout pattern of the photovoltaic module MC is as
illustrated in FIG. 6. On the layout, in the upper row, the
photovoltaic element D1a, the photovoltaic element D3c--the
photovoltaic element D2c, and the photovoltaic element D1h are
arranged from left to right in this order. In the middle row, the
photovoltaic element D2h, the photovoltaic element D1c--the
photovoltaic element D3f, and the photovoltaic element D2a are
arranged from left to right in this order. In the lower row, the
photovoltaic element D3a, the photovoltaic element D2f--the
photovoltaic element D1f, and the photovoltaic element D3h are
arranged from left to right in this order.
That is, the photovoltaic elements D are arranged such that the
layout pattern has a different arrangement from the arrangement on
the equivalent circuit. The layout pattern (FIG. 6) is an example,
and another layout pattern may be employed.
Assume that the shade SH shades the layout pattern of the
photovoltaic elements D (FIG. 6). That is, the shade SH provides
concentrated shades on the right edge of the middle row. That is,
the shade SH shades the photovoltaic element D1d, the photovoltaic
element D3f, and the photovoltaic element D2a. Accordingly, the
photovoltaic element D1d, the photovoltaic element D3f, and the
photovoltaic element D2a are in a non-generation state and do not
pass current (In the equivalent circuit of FIG. 5, the shade SH is
overlapped.).
In the state where the shade SH concentrates and shades the
photovoltaic element D1d, the photovoltaic element D3f, and the
photovoltaic element D2a, in the equivalent circuit, the
photovoltaic element D1d is arranged in the fourth position from
the left in the upper row, the photovoltaic element D2a is arranged
at the left end in the middle row, and the photovoltaic element D3f
is arranged in the third position from the right in the lower row.
Thus, these elements are decentrally arranged. That is, in each
straight rows (each of the upper row, the middle row, and the lower
row), there is only one photovoltaic element D in non-generation
state. The current restriction in series portions DS is limited to
a current restriction of one series portion DS.
Accordingly, in each straight row, only one photovoltaic element D
(the photovoltaic element D1d in the upper row, the photovoltaic
element D2a in the middle row, and the photovoltaic element D3f in
the lower row) is in non-generation state and restricts the entire
current. Substantially, the coupling condition that is not affected
by the shade SH becomes 3 (three elements in series).times.7 (seven
elements in parallel) in the equivalent circuit, and suppresses
decrease in power transmission efficiency on the current path.
That is, the photovoltaic module MC has the irradiated area rate of
21/24 (=0.875 that is the same as that of the photovoltaic module
MB.), the generating area rate of 21/24 (=0.875=87.5%), and the
power generation efficiency of 87.5% with respect to the whole
area.
That is, the photovoltaic module MC according to the present
invention ensures a large generating area rate even in the case
where the irradiated area rate is the same as that of the
photovoltaic module MB according to the present invention, and
suppresses decrease in power transmission efficiency. This improves
the power extraction efficiency, thus ensuring high power
generation efficiency as a whole. In the photovoltaic module MC,
the irradiated area rate and the generating area rate are the same.
This allows electric generation depending on sunshine and maintains
high power generation efficiency.
Next, advantageous effects of the photovoltaic module MB according
to the present invention with respect to the known photovoltaic
module MA will be further described. Here, the advantages of the
photovoltaic module MC with respect to the photovoltaic module MB
according to the present invention are as described above.
Therefore, an additional explanation will not be further
elaborated.
FIG. 7 is an equivalent circuit of the known photovoltaic module MA
in another embodiment. FIG. 8 is a pattern diagram schematically
illustrating a layout pattern of the photovoltaic module MA
illustrated in FIG. 7 and an assumed shade SH.
The photovoltaic module MA includes, for ease of comparison, three
elements in series and eight elements in parallel similarly to the
photovoltaic module MB. Assume that the shade SH shades the
photovoltaic element D1a arranged in the upper row of the series
portion DS, and the photovoltaic element D2f, the photovoltaic
element D2g, and the photovoltaic element D2h that are arranged in
the middle row (FIG. 8).
By the impact of the shade SH, the series portion DS coupled to the
photovoltaic element D1a, the series portion DS coupled to the
photovoltaic element D2f, the series portion DS coupled to the
photovoltaic element D2g, and the series portion DS coupled to the
photovoltaic element D2h are in a non-generation state.
That is, the series portions DS that ensure a generation state are
only four series portions DS coupled to the photovoltaic element
D1b, the photovoltaic element D1c, the photovoltaic element D1d,
and the photovoltaic element D1e.
Accordingly, the photovoltaic module MA has a generating area rate
(a ratio of area in a generation state, which allows output, to the
whole area) of 12/24 (=0.5=50%) despite an irradiated area rate of
20/24 (=0.83) and has a power generation efficiency of 50% with
respect to the area.
FIG. 9 is an equivalent circuit of a photovoltaic module MB to be
applied to the present invention. FIG. 10 is a pattern diagram
schematically illustrating a layout pattern of the photovoltaic
module MB illustrated in FIG. 9 and an assumed shade SH.
The photovoltaic module MB illustrated in FIG. 9 is different only
in the state of the shade SH, and otherwise similar to the
photovoltaic module MB illustrated in FIG. 3.
Regarding the shade SH, assume that the shade SH shades, similarly
to the case in FIG. 8, the photovoltaic element D1a arranged in the
upper row of the series portion DS, and the photovoltaic element
D2f, the photovoltaic element D2g, and the photovoltaic element D2h
that are arranged in the middle row (FIG. 10).
By the impact of the shade SH, the photovoltaic element D1a, the
photovoltaic element D2f, the photovoltaic element D2g, and the
photovoltaic element D2h are in a non-generation state. That is, in
the upper row, seven elements among the eight photovoltaic elements
D ensure a generation state. In the middle row, five elements among
the eight photovoltaic elements D ensure a generation state. In the
lower row, eight elements among the eight elements ensure a
generation state.
As described in FIG. 3 and FIG. 4, the entire current is restricted
by the straight row where the number of the photovoltaic elements D
in generation state among the respective straight rows is smallest.
Accordingly, in the middle row, the entire current is restricted by
the five elements (five columns) in generation state among the
eight elements. Substantially, five columns (3 rows.times.5
columns=15 photovoltaic elements D) are generation state. A ratio
of generating area to the whole area becomes 15/24.
Accordingly, the photovoltaic module MB has an irradiated area rate
of 20/24 (=0.83), a generating area rate (a ratio of area in a
generation state, which allows output, to the whole area) of 15/24
(=0.625=62.5%), and a power generation efficiency of 62.5% with
respect to the area.
That is, in the case where both the photovoltaic module MA and the
photovoltaic module MB have the same irradiated area rate (20/24
(=0.83)), the photovoltaic module MB has the generating area rate
of 62.5% while the photovoltaic module MA has the generating area
rate of 50%. Accordingly, the photovoltaic module MB improves the
power transmission efficiency to avoid an impact of the shade SH in
practical usage, and significantly improves the generating area
rate to improve the power extraction efficiency, compared with the
photovoltaic module MA.
Here, as described above, the photovoltaic module MC compared with
the photovoltaic module MB has higher power extraction
efficiency.
(Embodiment 1)
By referring to FIG. 11 to FIG. 16, a description will be given of
a photovoltaic module 10 included in a photovoltaic apparatus 1
(see Embodiment 2) according to the present invention as Embodiment
1.
FIG. 11 is a pattern diagram illustrating a coupling condition of a
photovoltaic element 11 in the photovoltaic module 10 applied to
Embodiment 1 of the present invention.
In the photovoltaic module 10, a plurality of series portions 12
are coupled in parallel. The series portion 12 includes a plurality
of photovoltaic elements 11 coupled in series. In the plurality of
the series portions 12, the respective photovoltaic elements 11
coupled in the same straight row are coupled in parallel.
The photovoltaic module 10 is preferred to employ a distributed
arrangement where a layout pattern of the photovoltaic elements 11
is different from the arrangement in the equivalent circuit. With
this configuration, the photovoltaic module 10 employs a
distributed arrangement as the layout pattern of the photovoltaic
elements 11 that constitute the photovoltaic module 10, so as to
suppress the impact of shade on the series portion 12 where the
photovoltaic elements 11 are coupled in series. This suppresses a
decrease in power transmission efficiency, thus improving power
extraction efficiency.
That is, the photovoltaic module 10 is preferred to have a
configuration similar to the photovoltaic module MB as described in
the column of "Configuration, and operation and effect of a
photovoltaic module to be applied to the present invention", or to
the photovoltaic module MC.
In the series portion 12, the respective photovoltaic elements 11
coupled in the same straight row are coupled in parallel by
parallel coupling lines 13. The photovoltaic elements 11 coupled in
series and in parallel are modularized by a mounting portion 15 in
a single mounting form as a whole. The photovoltaic module 10
includes a pair of output lines 14 as an external output unit. One
output line 14 is assigned to a positive side while the other
output line 14 is assigned to a negative side.
The inventors have discovered the following fact during examination
for a countermeasure to shade in a solar cell module (the
photovoltaic module 10). Compared with the form where the series
portions 12 with the photovoltaic elements 11 coupled in series are
coupled in parallel only at both ends of the series portions 12,
the arrangement form where the respective photovoltaic elements 11
in the same straight row are coupled in parallel provides extremely
advantageous characteristics for occurrence of shade (see FIG. 12
and the latter drawings). To more clearly describe the coupling
condition and the arrangement of the photovoltaic module 10 that
provides advantageous characteristics as the countermeasure for
shade, the present inventors express the coupling form of the
photovoltaic module 10 as "distributed arrangement
architecture."
For example, a total of 640 photovoltaic elements 11 are arranged
with 40 elements in series.times.16 elements in parallel. The
photovoltaic element 11 is, for example, a solar battery cell
formed on a silicon substrate or similar substrate. The solar
battery cell formed on the silicon substrate in a crystal system
has an open circuit voltage of about 0.6 V in a normal operating
state. Accordingly, if one photovoltaic element 11 provides an
output voltage of about 0.5 V (volts), 40 elements in series
provides an output (voltage) of about 20 V. That is, regarding the
photovoltaic elements 11, the number of elements in series and the
number of elements in parallel are set corresponding to an output
voltage to be requested. Output current increases proportionate to
the number of elements in parallel.
The mounting portion 15 typically includes, at its front surface
side, a singular translucent substrate (of a transparent material
in a planar shape or a curved surface shape) where the photovoltaic
elements 11 are arranged at its inner side. The photovoltaic
element 11 is, at a back surface side, protected by sealing
material to ensure weather resistance and mechanical strength.
The photovoltaic module 10 (the mounting portion 15) according to
this embodiment includes a temperature sensor 18 in addition to the
photovoltaic element 11. The temperature sensor 18 has a
configuration that obtains a temperature (a panel temperature Tp)
when the photovoltaic module 10 is operating. The temperature
sensor 18 is arranged, for example, at a gap between the
photovoltaic elements 11, and is preliminarily arranged to
accurately obtain an actual temperature of the photovoltaic element
11.
Regarding the temperature sensor 18, it is preferred that a
plurality of the temperature sensors 18 be evenly arranged as much
as possible with respect to the whole surface area of the mounting
portion 15. Regarding the temperature sensor 18, it is preferred
that a position where the temperature sensor 18 indicates a
temperature close to an average value among the temperatures in the
respective positions in the photovoltaic module 10 be preliminarily
selected and the temperature sensor 18 be disposed at the position.
The temperature sensor 18 is preferred to be arranged to directly
reflect an actual temperature of the photovoltaic element 11, for
example, arranged under the same condition as that of the
photovoltaic element 11 with respect to an irradiation light such
as sunlight.
If the photovoltaic element 11 is resin-sealed, the temperature
sensor 18 is preferred to be resin-sealed similarly to the
photovoltaic element 11. The temperature sensor 18 measures
(detects) a temperature in a state where the temperature sensor 18
is mounted close to the photovoltaic element 11 and similarly to
the photovoltaic element 11. This allows accurate measurement of
temperature (the panel temperature Tp) of the photovoltaic module
10 (the photovoltaic element 11).
The temperature sensor 18 is constituted by, for example, a
thermistor. The thermistor outputs a temperature as an electrical
signal, and has good consistency with the temperature range when a
solar battery cell or similar element to be applied as the
photovoltaic element 11 is operating. Accordingly, a highly
accurate temperature is detected, thus providing high reliability.
The temperature sensor 18 employs a thermocouple and similar
element other than the thermistor.
FIG. 12 is a characteristic graph illustrating a relationship of
extracted electric energy to irradiated area rate in the
photovoltaic module 10 illustrated FIG. 11
In FIG. 12, the horizontal axis denotes irradiated area rate (%)
and the vertical axis denotes extracted electric energy (a.u.: any
unit). The extracted electric energy of 100 (a.u.) corresponds to,
for example, the rated power (or maximum electric power). Change in
irradiated area rate corresponds to, in other words, what is called
change in shade.
The inventors have newly confirmed the following fact during
various examinations. The photovoltaic module 10 that employs the
distributed arrangement architecture shows a characteristic
completely different from that of the known photovoltaic module.
That is, the photovoltaic module 10 according to the embodiment
provides an output (the extracted electric energy) approximately
proportionate to the irradiated area rate. Accordingly, the
photovoltaic module 10 consistently prevents extreme decreases in
output even in a state where shade occurs, and ensures output
corresponding to the irradiated area rate.
FIG. 13 is a graph of an output characteristic illustrating
variation in output with respect to an output characteristic (a
power-voltage characteristic) of the photovoltaic module 10
illustrated in FIG. 11 in the case where a shaded condition is used
as a parameter.
In FIG. 13, the horizontal axis denotes voltage obtained from the
output line 14 of the photovoltaic module 10, and the vertical axis
denotes output (electric power) of the photovoltaic module 10
obtained by multiplication of voltage of the output line 14 and
current flowing into the output line 14. That is, the output
characteristic (the power-voltage characteristic) of the
photovoltaic module 10 is illustrated as a curved line in a bell
shape (a half-wave waveform) with a single peak from a voltage of
zero to an open circuit voltage Voc. Temperature (the panel
temperature Tp) is assumed to be constant.
The shaded conditions are classified into three parameters and
shown. Under a condition without shade, the relative maximum output
is obtained among the three conditions. Under the condition with
shade (large), the relative smallest output is obtained among the
three conditions. Under condition with shade (small), the
intermediate output is obtained among the three conditions. In
cases under the three shaded conditions, a difference between
respective outputs at the maximum power points, that is, an output
difference between the output (without shade) and output (with
shade (large)) is .DELTA.Pmx (S). A variation in output
corresponding to the shaded condition is observed.
With respect to the variation in output (.DELTA.Pmx (S)), a
difference between voltages (the maximum power operating voltage)
(.DELTA.Vpm (S)) corresponding to the maximum power points rarely
occurs. This shows the advantageous effect where the photovoltaic
module 10 receives little impact of shade (FIG. 12).
FIG. 14 is a characteristic graph illustrating variation in output
with respect to the output characteristic (the power-voltage
characteristic) of the photovoltaic module 10 illustrated in FIG.
11 in the case where a temperature condition is used as a
parameter.
In FIG. 14, the horizontal axis denotes voltage obtained from the
output line 14 of the photovoltaic module 10, and the vertical axis
denotes output (electric power) of the photovoltaic module 10
obtained by multiplication of voltage of the output line 14 and
current flowing into the output line 14. That is, the output
characteristic (the power-voltage characteristic) of the
photovoltaic module 10 is illustrated as a curved line in a bell
shape (a half-wave waveform) with a single peak from a voltage of
zero to an open circuit voltage Voc. Lighting intensity (existence
of the shade) is assumed to be constant.
The temperature conditions (the panel temperature Tp) are
classified into three parameters. Under a low temperature condition
(temperature (low)), the relatively maximum output is obtained
among the three conditions. Under a high temperature condition
(temperature (high)), the relatively smallest output is obtained
among the three conditions. Under an intermediate temperature
condition (temperature (intermediate)), the relatively intermediate
output is obtained among the three conditions. In cases under the
three temperature conditions, a difference between respective
outputs at the maximum power points, that is, a difference between
the output (temperature (low)) and output (temperature (high)) is
.DELTA.Pmx (Tp). The output is varied corresponding to the
temperature condition. That is, a lower temperature provides a
higher output.
With respect to the variation in output (.DELTA.Pmx (Tp)), a
difference between voltages (the maximum power operating voltage)
(.DELTA.Vpm (Tp)) corresponding to the maximum power points rarely
occurs. However, the distribution has the regularity of a magnitude
relationship within a certain range. That is, in the case where a
temperature is low, the maximum power operating voltage becomes
relatively high. The high temperature provides a relatively low
maximum power operating voltage. The open circuit voltage Voc
varies slightly corresponding to high and low of the temperature.
That is, in a state at high temperature, the open circuit voltage
Voc becomes low compared with a state at low temperature.
Accordingly, detecting a real temperature (a real panel temperature
RTp) of the photovoltaic module 10 allows relative comparison of an
output characteristic P-V (RTp) (see FIG. 19) approximated by an
output characteristic (the virtual output characteristic P-V (Tp),
see FIG. 19) at a preliminarily obtained panel temperature Tp. That
is, in the case where an MPPT control is performed (the maximum
power point tracking is performed) on the real output
characteristic P-V (RTp) of the photovoltaic module 10, this allows
an MPPT control of the real panel temperature RTp using the virtual
output characteristic P-V (Tp) (the details will be described in
Embodiment 2).
FIG. 15 is a data table illustrating an example where data is
obtained as a panel temperature-output correlation characteristic
with respect to the output characteristic illustrated in FIG. 14 to
make the listed data.
In FIG. 15, the column denotes panel temperature Tp (.degree. C.)
and the row denotes MPP (maximum power point) data that includes
the maximum output (Pmx) obtained from the photovoltaic module 10
and the maximum power operating voltage (Vpm) at the maximum output
(Pmx).
The panel temperature Tp varies depending on a position of the
photovoltaic module 10 to be arranged. Here, as a possible
temperature usually generated in a natural environment where, for
example, the photovoltaic module 10 is arranged and sunlight is
irradiated, for example, the MPP data for 0.degree. C. to
25.degree. C. to 50.degree. C. to 75.degree. C. and so on is
obtained as listed data.
If a value of the maximum power operating voltage Vpm corresponding
to the maximum output Pmx with respect to the panel temperature Tp
is obtained, the MPPT control in the photovoltaic apparatus 1
described in Embodiment 2 can be performed on the photovoltaic
module 10.
Hereinafter, a relationship between three portions of data (the
panel temperature Tp, the maximum output Pmx, and the maximum power
operating voltage Vpm) may be expressed as a (virtual) panel
temperature-output correlation characteristic P-V (Tp) (see FIG.
19). For the sake of simplification, the panel temperature-output
correlation characteristic P-V (Tp) may be described simply as an
output characteristic P-V (Tp). Additionally, in the case of the
real panel temperature RTp, it may be described as a panel
temperature-output correlation characteristic P-V (RTp) or an
output characteristic P-V (RTp).
While in FIG. 15 the data is exemplarily illustrated at intervals
of 25.degree. C., any temperature interval can be set and is
preferred to be set considering accuracy of the MPPT control,
search speed to be requested, and similar parameter.
In the case where the panel temperature Tp=0.degree. C., the
maximum output Pmx of a maximum output Pmx (0) and the maximum
power operating voltage Vpm of a maximum power operating voltage
Vpm (0) are used to obtain data. Hereinafter, similarly, for
example, in the case where the panel temperature Tp=75.degree. C.,
the maximum output Pmx (75) and the maximum power operating voltage
Vpm (75) are used to obtain data.
As the output characteristic illustrated in FIG. 14, a relationship
between the output characteristic (the power-voltage
characteristic: P-V characteristic) and the temperature (the panel
temperature Tp) in the photovoltaic module 10 has definite
regularity. Accordingly, the listed data in FIG. 15 is data where
the MPP data in the output characteristic with respect to the panel
temperature Tp, that is, the panel temperature-output correlation
characteristic is preliminarily obtained as a list and modeled.
Lighting intensity when the listed data in FIG. 15 is obtained is
preferred to be the maximum lighting intensity (assumed lighting
intensity) assumed under a condition where, for example, the
photovoltaic module 10 is assumed to operate. That is, in general
usage, since lighting intensity of a light irradiated to the
photovoltaic module 10 takes a value smaller than the assumed
lighting intensity, the photovoltaic module 10 has an output state
in numerical value smaller than the maximum output Pmx and the
maximum power operating voltage Vpm illustrated in FIG. 15.
That is, using the listed data illustrated in FIG. 15 allows simple
and highly accurate MPPT control of the photovoltaic module 10. The
listed data illustrated in FIG. 15 is registered as any data code
in a storage unit 23 (see FIG. 11) described in Embodiment 2, and
is read out to be used when the MPPT control is performed. Details
such as utilization of the MPP data will be described in Embodiment
2.
FIG. 16 is a data table illustrating a modification of the panel
temperature-output correlation characteristic where data is
obtained as a panel temperature-output correlation characteristic
with respect to the output characteristic illustrated in FIG. 14 to
make listed data.
A basic configuration of the modification of the panel
temperature-output correlation characteristic is similar to the
panel temperature-output correlation characteristic (the data
table) illustrated in FIG. 15. Accordingly, the main difference
will be described.
It is known that the maximum power operating voltage Vpm is
approximated by q.times.Voc where a unique element constant q
(here, q<1) determined by physicality (material and crystalline)
of the photovoltaic element (the solar battery cell) is multiplied
by the open circuit voltage Voc. For example, it is known that
q=0.8 in the case of crystal silicon solar cell and q=0.66 in the
case of amorphous silicon solar cell.
Accordingly, the open circuit voltage Voc is preliminarily stored
corresponding to the panel temperature Tp as data. An open circuit
voltage Voc corresponding to a measured panel temperature Tp is
employed to calculate a search start voltage Vt1 (see FIG. 19). The
formula for computation will be described in detail in Embodiment
2.
(Embodiment 2)
By referring to FIG. 17 to FIG. 19, descriptions will be given of
the photovoltaic apparatus 1 according to this embodiment, a
maximum power point tracking control method in the photovoltaic
apparatus 1, and a computer program that makes a computer execute
the maximum power point tracking control in the photovoltaic
apparatus 1. Here, the photovoltaic module 10 included in the
photovoltaic apparatus 1 is the photovoltaic module 10 described in
Embodiment 1.
FIG. 17 is a block diagram illustrating an overall configuration of
the photovoltaic apparatus 1 according to Embodiment 2 of the
present invention mainly using functional blocks.
FIG. 18 is a flowchart illustrating an operation process in a
tracking control device 20 that constitutes a main portion of the
photovoltaic apparatus 1 illustrated in FIG. 17.
FIG. 19 is a graph illustrating a state of maximum power point
tracking control in the tracking control device 20 that constitutes
the main portion of the photovoltaic apparatus 1 illustrated in
FIG. 17.
(Embodiment 2-1)
First, as (Embodiment 2-1), by referring mainly to FIG. 17 (the
functional blocks), a description will be given of the photovoltaic
apparatus 1 (here, FIG. 19 is referred as necessary).
The photovoltaic apparatus 1 according to this embodiment includes
a photovoltaic module 10 and a tracking control device 20. In the
photovoltaic module 10, a plurality of series portions 12 with a
plurality of photovoltaic elements 11 coupled in series are coupled
in parallel, and the photovoltaic elements 11 coupled in the same
straight row among the plurality of series portions 12 are coupled
parallel to one another. The tracking control device 20 performs a
maximum power point tracking control (MPPT control) at the output
of the photovoltaic module 10.
The photovoltaic module 10 includes a temperature sensor 18 that
detects a real panel temperature RTp that is a panel temperature Tp
when the photovoltaic module 10 is operating.
The tracking control device 20 includes, as basic data acquisition
units, a temperature information input unit 21, a voltage
information input unit 22v, and a current information input unit
22i. The temperature information input unit 21 acquires a
temperature (a panel temperature Tp, that is, a real panel
temperature RTp) detected by the temperature sensor 18 through a
signal line 18w. The voltage information input unit 22v acquires a
voltage value (an output voltage; a search voltage, or a set
voltage) of the photovoltaic module 10 output from an output line
14 through a signal line 16w. The current information input unit
22i acquires a current value (output current) of the photovoltaic
module 10 output from the output line 14 through the signal line
16w.
The tracking control device 20 includes, as a first main portion, a
storage unit 23, an output characteristic selecting unit 24, and a
search start setting unit 25.
In the storage unit 23, a panel temperature-output correlation
characteristic P-V (Tp) where a correlation relationship between
the panel temperature Tp and the output characteristic P-V (Tp) in
the photovoltaic module 10 is preliminarily specified is registered
as a plurality portions of listed data corresponding to the panel
temperature Tp (see FIG. 15 and FIG. 16). "Tp" in the panel
temperature-output correlation characteristic P-V (Tp) corresponds
to the temperature exemplarily illustrated in FIG. 15 and FIG. 16
as the data.
The output characteristic selecting unit 24 selects (extracts) one
panel temperature-output correlation characteristic P-V (Tp)
corresponding to the real panel temperature RTp among a plurality
of panel temperature-output correlation characteristics P-V (Tp) as
a virtual panel temperature-output correlation characteristic P-V
(Tp) (FIG. 19). Subsequently, the output characteristic selecting
unit 24 extracts (selects) a maximum power operating voltage Vpm0
corresponding to a maximum output Pmx in the virtual panel
temperature-output correlation characteristic P-V (Tp). Here, the
maximum power operating voltage Vpm0 may be described simply as,
for example, a maximum power operating voltage Vpm.
In the storage unit 23, the panel temperature Tp and the maximum
power operating voltage Vpm (Vpm0) corresponding to the maximum
output Pmx at the assumed lighting intensity are registered. This
allows a direct extraction of the maximum power operating voltage
Vpm corresponding to the real panel temperature RTp. Here, the
assumed lighting intensity is, as described above, preferred to be
the maximum lighting intensity assumed in an environment where the
photovoltaic module 10 operates. The maximum lighting intensity can
be obtained considering direct light and a similar parameter in
midsummer with respect to, for example, lighting intensity in
spring and fall. Alternatively, for each season (corresponding to
variation in altitude of sunlight), the assumed maximum lighting
intensity can be changed.
While in FIG. 19 the virtual panel temperature-output correlation
characteristic P-V (Tp) is illustrated as a curved line, any
configuration is possible insofar as three portions of data of the
maximum output Pmx, and the maximum power operating voltage Vpm and
the panel temperature Tp corresponding to the maximum output Pmx
are clear when the MPPT control is performed. The maximum output
Pmx is a target for comparison with the output characteristic P-V
(RTp) for the real panel temperature RTp.
In an actual operation state, the real panel temperature RTp may
have a different value from that of the panel temperature Tp
registered in the storage unit 23. That is, in the case where the
real panel temperature RTp is different from the panel temperature
Tp registered in the storage unit 23, the output characteristic
selecting unit 24 extracts a panel temperature-output correlation
characteristic P-V (Tp) corresponding to a panel temperature Tp
that is lower than and closest to the real panel temperature RTp
among the panel temperatures Tp registered in the storage unit 23
as the virtual panel temperature-output correlation characteristic
P-V (Tp).
With this configuration, the photovoltaic apparatus 1 extracts the
panel temperature-output correlation characteristic P-V (Tp)
corresponding to the panel temperature Tp that is lower than and
closest to the real panel temperature RTp among the panel
temperatures Tp registered in the storage unit 23 as the virtual
panel temperature-output correlation characteristic P-V (Tp). This
allows extraction of the virtual panel temperature-output
correlation characteristic P-V (Tp) to limit a search range of any
real panel temperature RTp to a narrow range and perform the
maximum power point tracking control.
The search start setting unit 25 extracts electric power from the
photovoltaic module 10 as a search electric power Pt1 when a search
is started in the case where a voltage of the photovoltaic module
10 is set to a search start voltage Vt1 (FIG. 19) that is a voltage
higher than the maximum power operating voltage Vpm0.
In the search start setting unit 25, setting of the search start
voltage Vt1 is performed as follows. By instruction of the search
start setting unit 25, any PWM signal is input from a search
control unit 28 to a power converter 30. The power converter 30 (a
DC-DC converter) regulates a voltage of the photovoltaic module 10
(the output line 14). Here, the PWM signal may be directly input
from the search start setting unit 25 to the power converter 30 not
through the search control unit 28. Additionally, the search start
setting unit 25 and the search control unit 28 may be integrated to
operate together.
Hereinafter, any additional character may be added corresponding to
a state of the search voltage Vt, for example, the search start
voltage Vt1, the search voltage Vt2, and so on. Additionally, if
the respective voltages specifically need not be distinguished from
one another, the search voltages may be described simply as search
voltages Vt. Additionally, the same applies to search electric
powers Pt (a search electric power Pt1, a search electric power
Pt2, and so on) corresponding to the search voltages Vt.
The search electric power Pt (such as the search electric power
Pt1, FIG. 19) is calculated by multiplication of a current value of
the current information input unit 22i and a voltage value (the
search start voltage Vt1) of the voltage information input unit 22v
that are obtained as output of the photovoltaic module 10 in a
state where the output of the photovoltaic module 10 is set to the
search voltage Vt (such as the search start voltage Vt1, FIG.
19).
The search start voltage Vt1 is calculated by a formula for
computation preliminarily specified with respect to the maximum
power operating voltage Vpm0 or the open circuit voltage Voc that
has a relative relationship with the maximum power operating
voltage Vpm0. With this configuration, the photovoltaic apparatus 1
calculates the search start voltage Vt1 by applying the formula for
computation to the maximum power operating voltage Vpm0 in the
virtual panel temperature-output correlation characteristic P-V
(Tp). This allows obtaining the search start voltage Vt1 accurately
and quickly even in any irradiation state of the photovoltaic
module 10.
Here, the formula for computation employs a formula (a formula for
computation 1) where a preliminarily specified margin voltage
.DELTA.Vm (FIG. 19) is added to the maximum power operating voltage
Vpm0 to specify the search start voltage Vt1, a formula (a formula
for computation 2) where a preliminarily specified rate
(coefficient) is multiplied by the maximum power operating voltage
Vpm0 to specify the search start voltage Vt1 that is a result of
the maximum power operating voltage Vpm0 with the addition of the
margin voltage .DELTA.Vm, and a formula (a formula for computation
3) where the search start voltage Vt1 is calculated based on the
open circuit voltage Voc. In FIG. 19, results (the margin voltages
.DELTA.Vm) of all the formulas for computation coincide with one
another.
In the formula for computation 1, the margin voltage .DELTA.Vm as
an absolute value is preliminarily assigned to the maximum power
operating voltage Vpm0 in the virtual panel temperature-output
correlation characteristic P-V (Tp), and is added to the maximum
power operating voltage Vpm0 to calculate the search start voltage
Vt1. Any value corresponding to an actual value of the maximum
power operating voltage Vpm0 may be set. For example, in the case
where the maximum power operating voltage Vpm0 is 20 V (volts), 22
V is set as the search start voltage Vt1 by, for example, adding
the margin voltage of 2 V as an absolute value. In this case, the
margin voltage .DELTA.Vm=2 V is preliminarily set. Similarly, in
the case where the maximum power operating voltage Vpm0 is 50 V,
for example, 5 V is added for calculation.
In the formula for computation 2, a coefficient k is multiplied by
the maximum power operating voltage Vpm0 in the virtual panel
temperature-output correlation characteristic P-V (Tp) to directly
calculate the search start voltage Vt1. That is, as the search
start voltage Vt1=k.times.the maximum power operating voltage Vpm0,
the calculation is performed. In the case where the coefficient
k>1, the calculation is the same as that in the case where the
margin voltage .DELTA.Vm is preliminarily added. In the case where
k=1.1, the search start voltage Vt1 is calculated as a result where
the margin voltage .DELTA.Vm of 10% is added to the maximum power
operating voltage Vpm0. Accordingly, in the case of the formula for
computation 2, the margin voltage .DELTA.Vm is expressed by the
search start voltage Vt1-the maximum power operating voltage
Vpm0.
For example, in the case where the maximum power operating voltage
Vpm0 is 20 V (volts), the search start voltage Vt1 of 22 V may be
set by multiplying 20 V by k=1.1. In this case, the margin voltage
.DELTA.Vm=the search start voltage Vt1-the maximum power operating
voltage Vpm0=2V is satisfied. Similarly, in the case where the
maximum power operating voltage Vpm0 is 50 V, the search start
voltage Vt1 is set to 55 V by multiplying 50 V by k=1.1.
The coefficient k is preferred to be around 1.2 at most such that a
result where the maximum power operating voltage Vpm is multiplied
by the coefficient k is equal to or less than the open circuit
voltage Voc. That is, in the case where the coefficient k is
expressed by 1<k.ltoreq.1.2, a voltage larger than the maximum
power operating voltage Vpm0 may be set as the search start voltage
Vt1. Additionally, a search range may be sufficiently limited. This
allows performing an accurate and quick search.
The formula for computation 2 calculates the search start voltage
Vt1 by multiplying the maximum power operating voltage Vpm0 by the
coefficient k. This allows directly applying the formula for
computation 2 even in the case where the maximum power operating
voltage Vpm0 varies depending on the specification of the
photovoltaic module 10. This ensures a versatile calculation
method. Additionally, even in the case where the maximum power
operating voltage Vpm0 completely varies depending on the
specification, this accurately determines the search start voltage
Vt1 with a constant ratio. This ensures a versatile process where
setting of the search start voltage Vt1 is stable.
As described above, the formula for computation 2 is preferred to
obtain the search start voltage Vt1 by multiplying the maximum
power operating voltage Vpm0 by the coefficient larger than one.
With this configuration, the photovoltaic apparatus 1 obtains the
search start voltage Vt1 by multiplying the maximum power operating
voltage Vpm0 by a coefficient larger than one. With any
specification of the maximum power operating voltage Vpm0 of the
photovoltaic module 10, this suppresses the impact of the
specification so as to extract an accurate search start voltage
Vt1.
In the formula for computation 3, the open circuit voltage Voc
extracted from the virtual panel temperature-output correlation
characteristic P-V (Tp) with respect to the panel temperature Tp is
applied to calculate the search start voltage Vt1. The formula for
computation 3 employs various computing equations as described
below.
The open circuit voltage Voc is multiplied by a unique element
constant q (see explanation of FIG. 16) to calculate the maximum
power operating voltage Vpm0. Subsequently, an operation for
calculating a numerical value between the maximum power operating
voltage Vpm0 and the open circuit voltage Voc is performed to
specify the search start voltage Vt1.
In the case where the formula for computation 3 is expressed as,
for example, (the open circuit voltage Voc+(the unique element
constant q.times.the open circuit voltage Voc))/2, (the open
circuit voltage Voc+the maximum power operating voltage Vpm0)/2 is
equivalently operated. Accordingly, the search start voltage Vt1
between the open circuit voltage Voc and the maximum power
operating voltage Vpm0 is calculated.
Alternatively, operating (the open circuit voltage Voc+the maximum
power operating voltage Vpm0)/2 as described above allows
calculating the search start voltage Vt1 directly from the open
circuit voltage Voc and the maximum power operating voltage Vpm0.
In this case, operation using the unique element constant q is not
necessary. This ensures a simpler operation.
The unique element constant q is preliminarily clear as a numerical
value indicative of a relationship between the open circuit voltage
Voc and the maximum power operating voltage Vpm by an element
structure. Accordingly, if a constant koc that satisfies
1>koc>q is preliminarily specified, applying the constant
koc.times.the open circuit voltage Voc=the search start voltage Vt1
as the formula for computation 3 allows calculating the search
start voltage Vt1 (the open circuit voltage Voc>the search start
voltage Vt1>the maximum power operating voltage Vpm0) based on
the open circuit voltage Voc.
In the case where the photovoltaic element is a single-crystal
silicon solar cell, Vpm0=q.times.Voc=0.8.times.Voc is satisfied.
Accordingly, Vpm (T)=0.8.times.Voc (T) is satisfied. Additionally,
in the case where the photovoltaic element is an amorphous silicon
solar cell, Vpm0=q.times.Voc=0.66.times.Voc is satisfied.
Similarly, Vpm (T)=0.66.times.Voc (T) is used to perform any
arithmetic processing.
A difference (a margin voltage .DELTA.Vm) between the maximum power
operating voltage Vpm0 extracted from the virtual panel
temperature-output correlation characteristic P-V (Tp) and the
search start voltage Vt1 calculated by operation on the maximum
power operating voltage Vpm0 is, in other words, to set a high
voltage with a constant margin (the margin voltage .DELTA.Vm) with
respect to the maximum power operating voltage Vpm0 as the search
start voltage Vt1. This allows extracting the maximum power point
(MPP) by a search in a preliminarily limited narrow range, thus
improving search accuracy and search speed.
Using a concrete example, as described above, on the maximum power
operating voltage Vpm0 extracted from the virtual panel
temperature-output correlation characteristic P-V (Tp), a search
within a narrow voltage range such as about 10% is performed to
extract and set the maximum power operating voltage Vpmn (see the
panel temperature-output correlation characteristic P-V (RTp) in
FIG. 19) with respect to the real panel temperature RTp. This
allows a quick tracking.
The tracking control device 20 starts a search using the search
start voltage Vt1 and the search electric power Pt1 when the search
is started as references, and extracts the maximum power point MPP
(RTp) of the photovoltaic module 10 at the real panel temperature
RTp (see FIG. 19). That is, the tracking control device 20 performs
the MPPT control that tracks the maximum power point MPP. The
tracking control device 20 obviously performs a search shifting to
a lower voltage side with respect to the search start voltage
Vt1.
As described above, the photovoltaic apparatus 1 according to this
embodiment performs a basic MPPT control using the storage unit 23,
the output characteristic selecting unit 24, and the tracking
control device 20.
Accordingly, the photovoltaic apparatus 1 according to this
embodiment detects the real panel temperature RTp of the
photovoltaic module 10 where the plurality of photovoltaic elements
11 are coupled in series and in parallel and the photovoltaic
elements 11 in the same straight row are coupled parallel to one
another, and extracts one panel temperature-output correlation
characteristic P-V (Tp) corresponding to the real panel temperature
RTp as the virtual panel temperature-output correlation
characteristic P-V (Tp). Accordingly, the photovoltaic apparatus 1
sets the voltage of the photovoltaic module 10 to the search start
voltage Vt1 higher than the maximum power operating voltage Vpm0 in
the virtual panel temperature-output correlation characteristic P-V
(Tp), and starts a search using the search start voltage Vt1 and
the search electric power Pt1 when the search is started as
references to perform the maximum power point tracking control.
This allows simple and accurate setting of the maximum power
operating voltage Vpmn in the detected real panel temperature RTp
using a search in a narrow range so as to simply, accurately, and
quickly track (search) the maximum power point MPP (RTp) (see FIG.
19) in the output characteristic P-V (RTp) of the photovoltaic
module 10.
In FIG. 19, the maximum power point MPP (Tp) in the virtual output
characteristic P-V (Tp) and the maximum power point MPP (RTp) in
the output characteristic P-V (RTp) at the real panel temperature
RTp have panel temperatures Tp close to each other as described
above, thus having a very approximate relationship as
characteristic curves. Additionally, since the panel temperature Tp
is lower than the real panel temperature RTp, the maximum power
operating voltage Vpm0 corresponding to the maximum power point MPP
(Tp) is slightly higher than the maximum power operating voltage
Vpmn corresponding to the maximum power point MPP (RTp). This
allows an assured search.
That is, as described in FIG. 13, in the same temperature state (at
the same panel temperature Tp), the maximum power operating voltage
Vpm0 and the maximum power operating voltage Vpmn have little
difference (the range corresponding to .DELTA.Vpm(S) in FIG. 13).
Accordingly, performing a search in an extremely limited narrow
search range (a range considering the difference between the
maximum power operating voltage Vpm0 and the maximum power
operating voltage Vpmn within a range from the maximum power
operating voltage Vpm0 to the search start voltage Vt1) allows
simple extraction of the maximum power operating voltage Vpmn for
an extremely simple and quick method of tracking the maximum power
point MPP (RTp).
The first main portion of the tracking control device 20 has been
described above. Next, a description will be given of a second main
portion of the tracking control device 20.
The tracking control device 20 includes a search processor 26, a
search power comparator 27, and the search control unit 28.
The search processor 26 extracts electric power from the
photovoltaic module 10 as a search electric power Pt2, a search
electric power Pt3 (not shown, same below), and so on for search
(FIG. 19). The extracted electric power is an electric power when
the search voltage Vt2, the search voltage Vt3, and so on for
search are set by sequentially decreasing the voltages of the
photovoltaic module 10 from the search start voltage Vt1, the
search voltage Vt2, the search voltage Vt3 (not shown, same below),
and so on by a preliminarily set search unit voltage .DELTA.Vs.
As the search electric power Pt with respect to the search voltage
Vt, there is a corresponding point on a curved line of the panel
temperature-output correlation characteristic P-V (RTp), which is
almost approximated as the virtual panel temperature-output
correlation characteristic P-V (Tp). That is, a search in the MPPT
control is performed on the curved line of the output
characteristic P-V (RTp).
In the first search, the search processor 26 calculates the search
voltage Vt2 by the formula for computation expressed by the search
voltage Vt2=the search start voltage Vt1-the search unit voltage
.DELTA.Vs, and controls the power converter 30 to set the search
voltage Vt2. Here, the setting of the search voltage Vt2 is
performed such that any PWM signal is input from the search control
unit 28 to the power converter 30 by instruction from the search
processor 26, and the power converter 30 regulates the voltage of
the photovoltaic module 10 (the output line 14). That is, the
voltage of the photovoltaic module 10 (the output line 14) is set
to the search voltage Vt2 by the control of the power converter
30.
The search processor 26 extracts the search electric power Pt2
after setting the search voltage Vt2. In the extraction of the
search electric power Pt2, signals from voltmeter and ammeter 16
are input to the current information input unit 22i through the
signal line 16w. Accordingly, the search electric power Pt2 is
calculated by obtaining a product of a current value obtained by
the current information input unit 22i and the search voltage Vt2.
That is, using the search voltage Vt2 as it is, the search electric
power Pt2 in the output characteristic P-V (RTp) is extracted.
In the setting of the search voltage Vt2, this allows inputting the
PWM signal from the search processor 26 directly to the power
converter 30 not through the search control unit 28. The search
processor 26 and the search control unit 28 may be integrated to
operate.
Hereinafter, a search after the second time is similarly performed.
That is, the second search is calculated as the search voltage
Vt3=the search voltage Vt2-the search unit voltage .DELTA.Vs. The
third search is calculated as the search voltage Vt4=the search
voltage Vt3-the search unit voltage .DELTA.Vs. Corresponding to the
calculated search voltage Vt, the output (output voltage) of the
photovoltaic module 10 (the output line 14) is set to the search
voltage Vt. Using the set search voltage Vt as it is, the search
electric power Pt is calculated.
The search unit voltage .DELTA.Vs is preferred to be set lower than
1/2 of the difference between the maximum power operating voltage
Vpm0 and the search start voltage Vt1. This configuration set the
search unit voltage .DELTA.Vs to a value smaller than 1/2 of the
difference between the maximum power operating voltage Vpm0 and the
search start voltage Vt10. Accordingly, when a search is performed
such that the search voltage Vt is decrementally shifted to a lower
side of the voltage by the search unit voltage .DELTA.Vs from the
search start voltage Vt1 to the maximum power operating voltage
Vpm0 side, the configuration allows performing at least a plurality
of searches between the search start voltage Vt1 and the maximum
power operating voltage Vpm0. This ensures a highly accurate and
quick search.
The search power comparator 27 compares (determine) the search
electric power Pt1, the search electric power Pt2, and so on before
the voltage of the photovoltaic module 10 is decreased by the
search unit voltage .DELTA.Vs, with the search electric power Pt2,
the search electric power Pt3, and so on when the voltage of the
photovoltaic module 10 is decreased by the search unit voltage
.DELTA.Vs.
That is, in the first search, the search electric power Pt1 at the
search start voltage Vt1 is compared with the search electric power
Pt2 at the search voltage Vt2. The magnitude relationship between
the search electric power Pt2 and the search electric power Pt1 is
compared. In the example illustrated in FIG. 19, the search
electric power Pt2-the search electric power Pt1=.DELTA.Pt>0 is
satisfied. Subsequently, the next (second) search is performed.
In the second search, the search electric power Pt2 at the search
voltage Vt2 is compared with the search electric power Pt3 (not
shown) at the search voltage Vt3 (not shown). The magnitude
relationship expressed by the search electric power Pt3 versus the
search electric power Pt2 is compared.
Hereinafter, the magnitude relationships for search electric power
Pt before and after the search voltage Vt is similarly decreased
are compared sequentially. Thus, MPPT control is performed.
Processes on the magnitude relationships of the search electric
powers Pt is performed by the search control unit 28 described
below.
In the case where the search electric power Pt1 before the voltage
of the photovoltaic module 10 is decreased by the search unit
voltage .DELTA.Vs is higher than the search electric power Pt2 when
the voltage of the photovoltaic module 10 is decreased by the
search unit voltage .DELTA.Vs (corresponding to the previous state
of the maximum power operating voltage Vpmn that is not illustrated
in FIG. 19), the search control unit 28 sets the voltage of the
photovoltaic module 10 before being decreased by the search unit
voltage .DELTA.Vs to the maximum power operating voltage Vpmn at
the real panel temperature RTp and terminates the search. In the
case where the search electric powers Pt1 (sequentially, the search
electric power Pt2 and so on) before the voltage of the
photovoltaic module 10 is decreased by the search unit voltage
.DELTA.Vs is lower than the search electric power Pt2
(sequentially, search electric power Pt3 and so on) when the
voltage of the photovoltaic module 10 is decreased by the search
unit voltage .DELTA.Vs, the search control unit 28 replaces the
search electric power Pt2 (sequentially, the search electric power
Pt3 and so on) at decreasing by the search unit voltage .DELTA.Vs
with the search electric power Pt1 (sequentially, search electric
power Pt2 and so on) before decreasing by the search unit voltage
.DELTA.Vs to perform the process in the search power comparator
27.
The above-described search is repeated to terminate the search at
the first decrement of the search unit voltage .DELTA.Vs that
decreases the search electric power Pt with respect to the maximum
power point MPP (RTp). This allows extracting the maximum power
operating voltage Vpmn in the output characteristic P-V (RTp)
within the extremely narrow range.
Accordingly, the photovoltaic apparatus 1, which includes the
search processor 26, the search power comparator 27, and the search
control unit 28, sequentially decreases the voltage from the search
start voltage Vt by the preliminarily set search unit voltage
.DELTA.Vs to be set to the search voltage Vt for search, and
compares the search electric powers Pt before and after the search
voltage Vt is changed by the search unit voltage .DELTA.Vs to
perform the maximum power point tracking control. This allows
efficient and quick setting of the maximum power operating voltage
Vpmn with respect to the real panel temperature RTp by the search
in the preliminarily set narrow range. Also in the case where the
irradiation state of the light is frequently varied, this allows
simple, accurate, and quick tracking of the maximum power point MPP
(RTp) in the output characteristic P-V (RTp) of the photovoltaic
module 10.
In the tracking control device 20, the functions and the coordinate
operations of the temperature information input unit 21, the
voltage information input unit 22v, the current information input
unit 22i, the storage unit 23, the output characteristic selecting
unit 24, the search start setting unit 25, the search processor 26,
the search power comparator 27, and the search control unit 28 as
described above are controlled by a tracking control unit 29.
That is, the tracking control unit 29 includes a central processing
unit (CPU). A computer program that coordinates and controls
operations from the temperature information input unit 21 to the
search control unit 28 is preliminarily installed. The computer
program is preliminarily stored in, for example, a program memory
to function the tracking control unit 29 at any timing.
Accordingly, the tracking control device 20 performs the MPPT
control on the photovoltaic module 10 in the photovoltaic apparatus
1 based on the computer program.
The panel temperature-output correlation characteristic P-V (Tp)
registered in the storage unit 23 associates the panel temperature
Tp with the maximum power operating voltage Vpm0 corresponding to
the maximum output Pmx, which is obtained by a preliminarily
assumed lighting intensity for a panel temperature Tp.
Accordingly, the photovoltaic apparatus 1 directly associates the
panel temperature Tp with the maximum power operating voltage Vpm0
corresponding to the maximum output Pmx at the panel temperature Tp
in the panel temperature-output correlation characteristic P-V
(Tp). Use of the virtual panel temperature-output correlation
characteristic P-V (Tp) corresponding to the detected real panel
temperature RTp allows an accurate and quick direct extraction of
the maximum power operating voltage Vpm0 of the photovoltaic module
10. This allows accurate and quick selection of the search start
voltage Vt1 to perform an accurate and quick maximum power point
tracking control.
The setting (setting the voltage that is the output of the
photovoltaic module 10) of the search voltages Vt (the search start
voltage Vt1, the search voltage Vt2, and so on) is, as described
above, performed as necessary based on the DC-DC converter included
in the power converter 30 and the voltage values obtained by the
voltage information input unit 22v. The extraction of the electric
power (the search electric power Pt1, the search electric power
Pt2, and so on) in the photovoltaic module 10 is calculated based
on the signal from the voltmeter and ammeter 16 by multiplication
of the current value extracted by the current information input
unit 22i and the voltage value extracted by the voltage information
input unit 22v.
The DC-DC converter (the power converter 30) has a configuration
that, for example, increases or decreases the output voltage of the
photovoltaic module 10. As a load of the power converter 30, a
battery BT constituted by a charging battery is coupled.
The DC-DC converter is controlled as necessary by a PWM signal that
is a control signal generated by the search control unit 28
(alternatively, as necessary, the search start setting unit 25 and
the search processor 26). The power converter 30 and the DC-DC
converter (the power converter 30) are operated by applying general
techniques. Thus, the details will not be further elaborated
here.
The search start voltage Vt1 (the search voltage Vt1) and the
search electric power Pt1 when the search is started are set to
points (for example, the search start voltage Vt1 is of 22 V where
the maximum power operating voltage Vpm0 is higher than 20 V by
10%) close to the maximum power operating voltage Vpm0 and the
maximum output Pmx at the panel temperature Tp (the closest panel
temperature Tp at low temperature side) corresponding to the real
panel temperature RTp to start the search. This allows quickly
performing the MPPT control in a narrow search range (several
volts).
In the maximum power point tracking control by the photovoltaic
apparatus 1 (the tracking control device 20) according to this
embodiment, the search range employs an extremely limited range.
This significantly decreases power consumption in the tracking
control device 20 and ensures an efficient photovoltaic apparatus
1.
(Embodiment 2-2)
Hereinafter, as (Embodiment 2-2), by referring mainly to FIG. 18,
descriptions will be given of a maximum power point tracking
control method in the photovoltaic apparatus 1 and a computer
program that allows a computer to execute the maximum power point
tracking control in the photovoltaic apparatus 1 (here, FIG. 19 is
referred as necessary).
Step S2:
The panel temperature Tp is measured. Here, in the case where a
plurality of temperature sensors 18 are used, temperatures obtained
from the respective temperature sensor 18 are simply averaged as
the panel temperature Tp (the real panel temperature RTp). The data
of the temperature sensor 18 is input to the temperature
information input unit 21 through the signal line 18w, and the real
panel temperature RTp is detected.
Step S4:
The output characteristic selecting unit 24 extracts and selects
the panel temperature-output correlation characteristic P-V (Tp)
(hereinafter, for the sake of simplification, referred to as the
output characteristic P-V (Tp) in some cases) corresponding to the
panel temperature Tp (the real panel temperature RTp) from the
storage unit 23. That is, the output characteristic P-V (Tp) of the
panel temperature Tp corresponding to the real panel temperature
RTp is selected from "panel temperature-output correlation
characteristic listed data" preliminarily registered in the storage
unit 23. The output characteristic P-V (Tp) is selected as the
virtual panel temperature-output correlation characteristic P-V
(Tp).
For example, in the case where the panel temperature Tp registered
in the storage unit 23 is 25.degree. C. and the detected real panel
temperature RTp is 26.degree. C., the respective panel temperatures
Tp do not coincide with each other. In the case where the panel
temperature Tp matching to the real panel temperature RTp is not
registered, the output characteristic P-V (Tp) (FIG. 19) at the
closest panel temperature Tp with respect to the real panel
temperature RTp at the low temperature side is selected. The
photovoltaic module 10 outputs a high electric power at the panel
temperature Tp of the low temperature side. On the maximum power
point MPP (RTp) and the maximum power operating voltage Vpmn (which
are not detected in this phase) in the output characteristic P-V
(RTp) that is a control target, an accurate and quick search is
performed in a narrow range from the high search voltage Vt side to
the low search voltage Vt side (from the low search electric power
Pt side to the high search electric power Pt side).
Step S6:
The output characteristic selecting unit 24 extracts (selects) the
maximum output Pmx at the maximum power point MPP (Tp) in the
selected output characteristic P-V (Tp), and the maximum power
operating voltage Vpm0 corresponding to the maximum output Pmx.
Hereinafter, descriptions of the panel temperature Tp and the real
panel temperature RTp are omitted in some cases.
Step S8:
The search start setting unit 25 calculates (determines) the search
start voltage Vt1 that is a voltage when the MPPT control is
started from the maximum power operating voltage Vpm0 extracted
based on the output characteristic P-V (Tp) (FIG. 19).
Additionally, the search start setting unit 25 makes the power
converter 30 control the output of the photovoltaic module 10, and
sets the voltage of the photovoltaic module 10 to the search start
voltage Vt1. That is, the search start setting unit 25 controls the
power converter 30 (the DC-DC converter) to set the voltage of the
solar cell module to the search voltage Vt1 (the search start
voltage Vt1).
The first search voltage Vt (the search start voltage Vt1) is, for
example, calculated (determined) as the search start voltage
Vt1=the coefficient k.times.the maximum power operating voltage
Vpm0. Regardless of the coefficient k, a preliminarily specified
absolute value may be added for calculation. By referring to the
open circuit voltage Voc, the search start voltage Vt1 may be
calculated.
Step S10:
The search start setting unit 25 measures current at the set search
start voltage Vt1 to obtain the output (the electric power) of the
photovoltaic module 10. The obtained output is calculated as the
search electric power Pt1 when starting the search.
Step S12:
The search processor 26 performs arithmetic processing (subtraction
in this embodiment) using the search unit voltage .DELTA.Vs (FIG.
19) on the search voltage Vt before the operation in this step is
performed to calculate (determine) the next search voltage Vt. A
computing equation is expressed by the previous search voltage
Vt-the search unit voltage .DELTA.Vs=the next search voltage Vt.
Specifically, the search voltage Vt2 in the first search=the search
start voltage Vt1-the search unit voltage .DELTA.Vs is satisfied.
The search voltage Vt3 in the second search=Vt2-.DELTA.Vs is
satisfied. The search voltage Vtn4 in the third
search=Vt3-.DELTA.Vs is satisfied. The search voltage Vt3, the
search voltage Vtn4, and so on are not illustrated.
The search unit voltage .DELTA.Vs is preliminarily set. The search
unit voltage .DELTA.Vs is necessary to be lower than at least the
margin voltage .DELTA.Vm. That is, the search unit voltage
.DELTA.Vs is preferred to have extent of a value that allows
performing searches at least several times within the range of the
margin voltage .DELTA.Vm (the search start voltage Vt1 to the
maximum power operating voltage Vpm0).
The search unit voltage .DELTA.Vs can also be obtained by
multiplying the margin voltage .DELTA.Vm by the coefficient q
(1>q (for example, q=0.3)>0) that is smaller than one. That
is, the calculation may be performed by the search unit voltage
.DELTA.Vs=q.times.the margin voltage .DELTA.Vm. Use of the
coefficient q applied to the multiplication allows a simple and
accurate determination (calculation) about the search unit voltage
.DELTA.Vs even in the case where, for example, the maximum power
operating voltage Vpm varies depending on the photovoltaic module
10.
While the search unit voltage .DELTA.Vs is described as a fixed
value, the search unit voltage .DELTA.Vs may be set as a variable
value to be sequentially decreased. Setting as the variable value
to be sequentially decreased allows a quicker and more accurate
performance of the MPPT control.
The search processor 26 sets the voltage of the photovoltaic module
10 to the next search voltage Vt obtained by calculation. Similarly
to the case of the search start voltage Vt1, the power converter 30
controls the voltage of the photovoltaic module 10.
Hereinafter, the search voltage Vt3, the search voltage Vt4, and so
on are sequentially set.
Step S14:
The search processor 26 sequentially measures currents at the set
search voltages Vt (Vt1, Vt2, Vt3, and so on), and calculates
(extracts) the next search electric powers Pt (Pt1, Pt2, Pt3 (the
rest is not shown), and so on).
Step S16:
The search power comparator 27 determines whether or not the
calculated next search electric power Pt is higher than the
previous search electric power Pt. For example, in the case where
the n-th search and the (n+1)-th search are performed, "the next
search electric power Ptn (n=n+1)" and "the previous search
electric power Ptn" are compared.
In the case where the next search electric power Ptn (n=n+1) is
higher than the previous search electric power Ptn (YES in step
S16), the process proceeds to S18. Additionally, in the case where
"the next search electric power Ptn (n=n+1)" is lower than "the
previous search electric power Ptn" (NO in step S16), the process
proceeds to S20.
Step S18:
The search control unit 28 replaces the search electric power Ptn
before being decreased by the search unit voltage .DELTA.Vs with
the next search electric power Ptn (n=n+1) calculated when being
decreased by the search unit voltage .DELTA.Vs. The process then
returns to step S12.
Step S20:
The search control unit 28 sets the search voltage Vtn at the
previous search electric power Ptn to a new maximum power operating
voltage Vpmn, and terminates the MPPT control.
As described above, this embodiment is performed as the maximum
power point tracking control method in the photovoltaic apparatus
1.
That is, the maximum power point tracking control method in the
photovoltaic apparatus 1 according to this embodiment is a maximum
power point tracking control method in the photovoltaic apparatus 1
that includes a photovoltaic module 10 and a tracking control
device 20. The photovoltaic module 10 includes a plurality of
series portions 12 coupled in parallel. The series portion 12
includes a plurality of photovoltaic elements 11 coupled in series.
The photovoltaic elements 11 coupled in a same straight row of the
plurality of series portions 12 are coupled parallel to one
another. The tracking control device 20 is configured to perform a
maximum power point tracking control on an output of the
photovoltaic module 10. In the maximum power point tracking control
method, the photovoltaic module 10 includes a temperature sensor
18. The temperature sensor 18 is configured to detect a real panel
temperature RTp. The real panel temperature RTp is a panel
temperature Tp when the photovoltaic module 10 is operating. The
tracking control device 20 includes a storage unit 23, an output
characteristic selecting unit 24, and a search start setting unit
25. In the storage unit 23, a plurality of panel temperature-output
correlation characteristics P-V (Tp) are registered corresponding
to the panel temperature Tp. The panel temperature-output
correlation characteristic P-V (Tp) preliminarily specifies a
correlation relationship between the panel temperature Tp and the
output characteristic P-V (Tp) in the photovoltaic module 10.
Additionally, the maximum power point tracking control method
includes: a step of detecting a real panel temperature RTp by the
temperature sensor 18 (step S2); a step of extracting one of the
panel temperature-output correlation characteristics P-V (Tp)
corresponding to the real panel temperature RTp among the plurality
of panel temperature-output correlation characteristics P-V (Tp) as
a virtual panel temperature-output correlation characteristic P-V
(Tp), and selecting a maximum power operating voltage Vpm0
corresponding to a maximum output in the virtual panel
temperature-output correlation characteristic P-V (Tp) by the
output characteristic selecting unit 24 (step S4 and step S6); a
step of extracting an electric power of the photovoltaic module 10
when a voltage of the photovoltaic module 10 is set to a search
start voltage Vt1 higher than the maximum power operating voltage
Vpm0 as a search electric power Pt1 when a search is started, by
the search start setting unit 25 (step S8 and step S10); and a step
of starting a search using the search start voltage Vt1 and the
search electric power Pt1 when the search is started, as
references, and a step of extracting a maximum power point MPP
(RTp) of the photovoltaic module 10 at the real panel temperature
RTp by the tracking control device 20 (step S12 to step S20).
Thus, the maximum power point tracking control method in the
photovoltaic apparatus 1 according to the present invention
includes: detecting a real panel temperature RTp of the
photovoltaic module 10; selecting a maximum power operating voltage
Vpm corresponding to a maximum output in the virtual panel
temperature-output correlation characteristic P-V (Tp); extracting
an electric power of the photovoltaic module 10 when a voltage of
the photovoltaic module 10 is set to a search start voltage Vt1
higher than the maximum power operating voltage Vpm0 as a search
electric power Pt1 when a search is started; then starting a search
using the search start voltage Vt1 and the search electric power
Pt1 when the search is started as references; and extracting a
maximum power point MPP (RTp) of the photovoltaic module 10 at the
real panel temperature RTp. This allows a simple and accurate
setting of the maximum power operating voltage Vpmn at the detected
real panel temperature RTp by a search in a narrow range, thus
ensuring a simple, accurate, and quick tracking (searching) of the
maximum power point MPP (RTp) of the output characteristic P-V
(RTp) in the photovoltaic module 10.
With the maximum power point tracking control method in the
photovoltaic apparatus 1 according to this embodiment, the search
start voltage Vt1 higher than the maximum power operating voltage
Vpm0 corresponding to the maximum output Pmx in the virtual panel
temperature-output correlation characteristic P-V (Tp) is set to
perform a search. This search with the narrow range allows setting
the maximum power operating voltage Vpmn at the real panel
temperature RTp by the search with the narrow range. This
suppresses power consumption of the tracking control device 20 in
the maximum power point tracking control, thus performing a quick
and efficient control.
In the maximum power point tracking control method in the
photovoltaic apparatus 1 according to this embodiment, the tracking
control device 20 in the photovoltaic apparatus 1 includes the
search processor 26, the search power comparator 27, and the search
control unit 28.
That is, the maximum power point tracking control method according
to this embodiment includes: a step of extracting the electric
power of the photovoltaic module 10 as a search electric power Pt
for search by a search processor 26, the electric power being
obtained when a voltage of the photovoltaic module 10 is
sequentially decreased from the search start voltage Vt1 by a
preliminarily set search unit voltage .DELTA.Vs every time so as to
be set to a search voltage for search (step S12 and step S14); a
step of comparing the search electric power Ptn before the voltage
of the photovoltaic module 10 is decreased by the search unit
voltage .DELTA.Vs with the search electric power Ptn (n=n+1) when
the voltage of the photovoltaic module 10 is decreased by the
search unit voltage by a search power comparator 27 (step S16); and
a step of setting the voltage of the photovoltaic module 10 before
decreasing by the search unit voltage .DELTA.Vs to a maximum power
operating voltage Vpmn at the real panel temperature RTp and
terminating the search in the case where the search electric power
Ptn before the voltage of the photovoltaic module 10 is decreased
by the search unit voltage .DELTA.Vs is higher than the search
electric power Ptn (n=n+1) when the voltage of the photovoltaic
module 10 is decreased by the search unit voltage .DELTA.Vs, and
replacing the search electric power Ptn before decreasing by the
search unit voltage .DELTA.Vs with the search electric power Ptn
(n=n+1) when decreasing by the search unit voltage .DELTA.Vs so as
to perform a subsequent process in the search power comparator 27
by a search control unit 28 in the case where the search electric
power Ptn before the voltage of the photovoltaic module 10 is
decreased by the search unit voltage .DELTA.Vs is lower than the
search electric power Ptn (n=n+1) when the voltage of the
photovoltaic module 10 is decreased by the search unit voltage
.DELTA.Vs (step S18 and step S20).
Accordingly, the maximum power point tracking control method in the
photovoltaic apparatus 1 according to this embodiment efficiently
and quickly sets the maximum power operating voltage Vpm0
corresponding to the real panel temperature RTp by the search with
the preliminarily set narrow range. Even in the case where the
irradiation state of the light is frequently varied, this allows a
simple, accurate, and quick tracking of the maximum power point MPP
(RTp) in the output characteristic P-V (RTp) of the photovoltaic
module 10.
As described above, this embodiment is provided as a computer
program that makes a computer execute the maximum power point
tracking control in the photovoltaic apparatus 1.
The computer program according to this embodiment is a computer
program for a computer to execute a maximum power point tracking
control in the photovoltaic apparatus 1 that includes a
photovoltaic module 10 and a tracking control device 20. The
photovoltaic module 10 includes a plurality of series portions 12
coupled in parallel. The series portion 12 includes a plurality of
photovoltaic elements 11 coupled in series. The photovoltaic
elements 11 coupled in a same straight row of the plurality of
series portions 12 are coupled parallel to one another. The
tracking control device 20 is configured to perform a maximum power
point tracking control on an output of the photovoltaic module 10.
The photovoltaic module 10 includes a temperature sensor 18. The
temperature sensor 18 is configured to detect a real panel
temperature RTp. The real panel temperature RTp is a panel
temperature Tp when the photovoltaic module 10 is operating. The
tracking control device 20 includes a storage unit 23 where a
plurality of panel temperature-output correlation characteristics
P-V (Tp) are registered corresponding to the panel temperature Tp,
an output characteristic selecting unit 24, and a search start
setting unit 25. The panel temperature-output correlation
characteristic P-V (Tp) preliminarily specifies a correlation
relationship between the panel temperature Tp and the output
characteristic P-V (Tp) in the photovoltaic module 10. The computer
program causes a computer execute: a step of detecting a real panel
temperature RTp using the temperature sensor 18 by the tracking
control device 20 (step S2); a step of extracting one of the panel
temperature-output correlation characteristics P-V (Tp)
corresponding to the real panel temperature RTp among the plurality
of panel temperature-output correlation characteristics P-V (Tp) as
a virtual panel temperature-output correlation characteristic P-V
(Tp), and selecting a maximum power operating voltage Vpm0
corresponding to a maximum output in the virtual panel
temperature-output correlation characteristic P-V (Tp) by the
output characteristic selecting unit 24 (step S4 and step S6); a
step of extracting an electric power of the photovoltaic module 10
when a voltage of the photovoltaic module 10 is set to a search
start voltage Vt1 higher than the maximum power operating voltage
Vpm0 as a search electric power Pt1 when a search is started, by
the search start setting unit 25 (step S8 and step S10); and a step
of starting a search using the search start voltage Vt1 and the
search electric power Pt1 when the search is started as references,
and extracting a maximum power point MPP (RTp) of the photovoltaic
module 10 at the real panel temperature RTp by the tracking control
device 20 (step S12 to step S20).
Accordingly, the computer program, which makes the computer execute
the maximum power point tracking control in the photovoltaic
apparatus 1 according to this embodiment, makes the computer
execute the maximum power point tracking control method in the
photovoltaic apparatus 1 according to the present invention. This
allows a simple and accurate setting of the maximum power operating
voltage Vpmn at the detected real panel temperature RTp by a search
in a narrow range, thus ensuring a simple, accurate, and quick
tracking (searching) of the maximum power point MPP (RTp) of the
output characteristic P-V (RTp) in the photovoltaic module 10.
In the computer program according to this embodiment, the tracking
control device 20 in the photovoltaic apparatus 1 includes the
search processor 26, the search power comparator 27, and the search
control unit 28.
That is, the computer program for the computer according to this
embodiment executes: a step of extracting extracts the electric
power of the photovoltaic module 10 as a search electric power Pt
for search where the electric power is obtained when a voltage of
the photovoltaic module 10 is sequentially decreased from the
search start voltage Vt1 by a preliminarily set search unit voltage
.DELTA.Vs every time so as to be set to a search voltage for search
by a search processor 26 (step S12 and step S14); a step of
comparing the search electric power Ptn before the voltage of the
photovoltaic module 10 is decreased by the search unit voltage
.DELTA.Vs with the search electric power Ptn (n=n+1) when the
voltage of the photovoltaic module is decreased by the search unit
voltage .DELTA.Vs by a search power comparator 27 (step S16); and a
step of setting the voltage of the photovoltaic module 10 before
decreasing by the search unit voltage .DELTA.Vs to a maximum power
operating voltage Vpmn at the real panel temperature RTp and
terminating the search in the case where the search electric power
Ptn before the voltage of the photovoltaic module 10 is decreased
by the search unit voltage .DELTA.Vs is higher than the search
electric power Ptn (n=n+1) when the voltage of the photovoltaic
module 10 is decreased by the search unit voltage .DELTA.Vs, and
replacing the search electric power Ptn before decreasing by the
search unit voltage .DELTA.Vs with the search electric power Ptn
(n=n+1) when decreasing by the search unit voltage .DELTA.Vs so as
to perform a subsequent process in the search power comparator 27
by a search control unit 28 in the case where the search electric
power Ptn before the voltage of the photovoltaic module 10 is
decreased by the search unit voltage .DELTA.Vs is lower than the
search electric power Ptn (n=n+1) when the voltage of the
photovoltaic module 10 is decreased by the search unit voltage
.DELTA.Vs (step S18 and step S20).
Accordingly, the computer program that makes the computer execute
the maximum power point tracking control in the photovoltaic
apparatus 1 according to the present invention efficiently and
quickly sets the maximum power operating voltage Vpm0 corresponding
to the real panel temperature RTp by the search with the
preliminarily set narrow range. Even in the case where the
irradiation state of the light is frequently varied, this allows a
simple, accurate, and quick tracking of the maximum power point in
the output characteristic P-V (RTp) of the photovoltaic module
10.
(Embodiment 3)
By referring to FIG. 20, a description will be given of a moving
body 50 according to the present invention. On the moving body 50,
the photovoltaic apparatus 1 according to Embodiment 1 or
Embodiment 2 is mounted.
FIG. 20 is a block diagram illustrating functional blocks of the
moving body 50 according to Embodiment 3 of the present
invention.
The moving body 50 according to this embodiment includes a
photovoltaic apparatus, a cell power supply (a main battery B.TM.,
a sub battery BTs, and a battery coordination unit BTc that
controls a coordination between the main battery B.TM. and the sub
battery BTs), and a motor 56. The photovoltaic apparatus includes a
photovoltaic module 51 (corresponding to the photovoltaic module 10
according to Embodiment 1) and a MPPT control unit 52
(corresponding to the tracking control device 20 according to
Embodiment 2) as a tracking control device that performs the
maximum power point tracking control (MPPT control) on the output
of the photovoltaic module 51. The cell power supply is charged by
the photovoltaic apparatus (the photovoltaic module 51 and the MPPT
control unit 52). The motor 56 operates by electric power supplied
from the cell power supply. The motor 56 allows the moving body 50
to run.
The sub battery BTs is an electric power supply for a sub control
unit 53 while the main battery BTm is an electric power supply for
a main control unit 54. The sub control unit 53 controls, for
example, a lamp LP and similar member used in a signaling system
that is not related to a drive system. The main control unit 54
controls an inverter 55 using the electric power supplied from the
main battery BTm. The inverter 55 drives the motor 56 to rotate a
driving shaft 58 coupled to a wheel 57. Accordingly, the mounted
photovoltaic apparatus (the photovoltaic module 51 and the MPPT
control unit 52) allows the moving body 50 to run. The photovoltaic
apparatus corresponds to the photovoltaic apparatus 1 according to
Embodiment 2. The moving body 50 specifically corresponds to an
electric vehicle (an electric car).
Accordingly, the moving body 50 according to the present invention
includes the photovoltaic apparatus (the photovoltaic apparatus 1
according to Embodiment 2). This photovoltaic apparatus operates
with the maximum output by the maximum power point tracking control
corresponding to the real panel temperature RTp that is the panel
temperature Tp when the photovoltaic module 10 is operating. The
moving body 50 performs a quick and efficient maximum power point
tracking control and suppresses power consumption in the control
system caused by the maximum power point tracking control. This
eliminates the impact of the shade during running to ensure a
stable efficient electric generation and running.
The photovoltaic apparatus 1 ensures a control with extremely low
power consumption in the maximum power point tracking control.
Thus, applying the photovoltaic apparatus 1 to the moving body 50
provides a significant effect where the cell power supply is
effectively utilized.
Operation and effect in the moving body 50 according to this
embodiment will be supplementarily described below.
In an automobile or other vehicles during running, the shade is not
constant. A state of the shade varies from moment to moment
depending on a moving condition. Accordingly, applying the MPPT
tracking control by a known simple hill-climbing method (a known
algorithm) is practically impossible.
For example, the moving body running at 60 km per hour moves 1 m
per 60 ms (msec). In the case where an MPP detection algorithm in
the general hill-climbing method is applied, a clock frequency in a
microcomputer (the tracking control device 20) is set to about 100
Hz to 200 kHz in the detection of the MPP. The MPP detection
requires time of at least several tens of ms (msec). If the MPP
detection is performed while the vehicle is running, the vehicle
moves several m (meters) from start to completion of the detection.
Accordingly, it is substantially difficult to perform an accurate
MPP detection.
In contrast, in the photovoltaic module 10 employed in the moving
body 50 according to this embodiment, the position of the maximum
power operating voltage Vpm in the output characteristic P-V hardly
varies depending on the state of the shade. Additionally, the panel
temperature Tp of the photovoltaic module 10 hardly varies in a
short time due to the state of the shade. Accordingly, the
detection of the panel temperature Tp (the real panel temperature
RTp) by the temperature sensor 18 allows a sufficiently efficient,
and highly accurate MPPT control.
Especially, in the case where the photovoltaic module 10 has a
constant size and integrally implemented, heat capacity becomes
larger. The photovoltaic module 10 is hardly affected by
temperature change, and does not generate a rapid temperature
change due to variation in the external environment (in the sun/in
the shade) during running.
Accordingly, in the moving body 50, this allows detecting the MPP
using a simple MPP detection algorithm. That is, compared with the
MPP detection by the general hill-climbing method, this decreases
calculation amount and makes calculation speed faster. Thus, this
significantly decreases power consumption in the tracking control
device 20. In other words, this increases power generation amount
(extracted electric energy) in the whole photovoltaic apparatus
(the photovoltaic module 51 and the MPPT control unit 52), which
includes the tracking control device 20.
The present invention can be embodied and practiced in other
different forms without departing from the spirit and essential
characteristics of the present invention. Therefore, the
above-described embodiments are considered in all respects as
illustrative and not restrictive. The scope of the invention is
indicated by the appended claims rather than by the foregoing
description. All variations and modifications falling within the
equivalency range of the appended claims are intended to be
embraced therein.
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